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 $86.91   10.414%   $95.9608   $95.96   $95.95   $96.00  
  Purchase #2 $163.45   13.562%   $185.6171   $185.62   $185.60   $185.60  
  Purchase #3 $58.50   13.434%   $66.3589   $66.36   $66.35   $66.40  
  Purchase #4 $98.26   13.138%   $111.1694   $111.17   $111.15   $111.20  
  Purchase #5 $162.33   7.353%   $174.2661   $174.27   $174.25   $174.30  
  Purchase #6 $44.49   7.161%   $47.6759   $47.68   $47.70   $47.70  
  Purchase #7 $204.71   13.577%   $232.5035   $232.50   $232.50   $232.50  
  7 purchase totals = $818.65       $913.5517   $913.56   $913.50   $913.70