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 $230.36   13.175%   $260.7099   $260.71   $260.70   $260.70  
  Purchase #2 $227.92   6.137%   $241.9075   $241.91   $241.90   $241.90  
  Purchase #3 $211.50   11.754%   $236.3597   $236.36   $236.35   $236.40  
  Purchase #4 $189.66   3.739%   $196.7514   $196.75   $196.75   $196.80  
  Purchase #5 $93.85   9.855%   $103.0989   $103.10   $103.10   $103.10  
  Purchase #6 $214.96   3.763%   $223.0489   $223.05   $223.05   $223.00  
  Purchase #7 $189.78   8.200%   $205.342   $205.34   $205.35   $205.30  
  7 purchase totals = $1,358.03       $1,467.2183   $1,467.22   $1,467.20   $1,467.20