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 $195.35   3.283%   $201.7633   $201.76   $201.75   $201.80  
  Purchase #2 $80.36   6.600%   $85.6638   $85.66   $85.65   $85.70  
  Purchase #3 $66.66   8.450%   $72.2928   $72.29   $72.30   $72.30  
  Purchase #4 $89.31   6.523%   $95.1357   $95.14   $95.15   $95.10  
  Purchase #5 $18.73   5.470%   $19.7545   $19.75   $19.75   $19.80  
  Purchase #6 $94.99   3.638%   $98.4457   $98.45   $98.45   $98.40  
  Purchase #7 $138.86   10.299%   $153.1612   $153.16   $153.15   $153.20  
  7 purchase totals = $684.26       $726.2170   $726.21   $726.20   $726.30