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 $59.48   8.740%   $64.6786   $64.68   $64.70   $64.70  
  Purchase #2 $175.60   3.481%   $181.7126   $181.71   $181.70   $181.70  
  Purchase #3 $113.88   5.682%   $120.3507   $120.35   $120.35   $120.40  
  Purchase #4 $172.31   11.268%   $191.7259   $191.73   $191.75   $191.70  
  Purchase #5 $188.82   4.704%   $197.7021   $197.70   $197.70   $197.70  
  Purchase #6 $197.68   5.525%   $208.6018   $208.60   $208.60   $208.60  
  Purchase #7 $226.35   10.165%   $249.3585   $249.36   $249.35   $249.40  
  7 purchase totals = $1,134.12       $1,214.1302   $1,214.13   $1,214.15   $1,214.20