Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $202.47   10.494%   $223.7172   $223.72   $223.70   $223.70  
  Purchase #2 $202.61   13.696%   $230.3595   $230.36   $230.35   $230.40  
  Purchase #3 $197.26   10.439%   $217.852   $217.85   $217.85   $217.90  
  Purchase #4 $139.48   9.588%   $152.8533   $152.85   $152.85   $152.90  
  Purchase #5 $203.93   13.123%   $230.6917   $230.69   $230.70   $230.70  
  Purchase #6 $151.37   9.795%   $166.1967   $166.20   $166.20   $166.20  
  Purchase #7 $250.77   3.843%   $260.4071   $260.41   $260.40   $260.40  
  7 purchase totals = $1,347.89       $1,482.0775   $1,482.08   $1,482.05   $1,482.20