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 $87.93   8.353%   $95.2748   $95.27   $95.25   $95.30  
  Purchase #2 $159.84   8.519%   $173.4568   $173.46   $173.45   $173.50  
  Purchase #3 $216.57   11.717%   $241.9455   $241.95   $241.95   $241.90  
  Purchase #4 $214.86   12.539%   $241.8013   $241.80   $241.80   $241.80  
  Purchase #5 $159.79   5.224%   $168.1374   $168.14   $168.15   $168.10  
  Purchase #6 $96.51   4.603%   $100.9524   $100.95   $100.95   $101.00  
  Purchase #7 $205.45   11.576%   $229.2329   $229.23   $229.25   $229.20  
  7 purchase totals = $1,140.95       $1,250.8011   $1,250.80   $1,250.80   $1,250.80