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 $91.49   6.629%   $97.5549   $97.55   $97.55   $97.60  
  Purchase #2 $148.42   10.385%   $163.8334   $163.83   $163.85   $163.80  
  Purchase #3 $44.41   10.680%   $49.153   $49.15   $49.15   $49.20  
  Purchase #4 $45.71   9.209%   $49.9194   $49.92   $49.90   $49.90  
  Purchase #5 $187.46   4.226%   $195.3821   $195.38   $195.40   $195.40  
  Purchase #6 $245.93   8.208%   $266.1159   $266.12   $266.10   $266.10  
  Purchase #7 $60.86   7.395%   $65.3606   $65.36   $65.35   $65.40  
  7 purchase totals = $824.28       $887.3193   $887.31   $887.30   $887.40