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 $94.73   3.401%   $97.9518   $97.95   $97.95   $98.00  
  Purchase #2 $250.76   8.244%   $271.4327   $271.43   $271.45   $271.40  
  Purchase #3 $142.65   5.179%   $150.0378   $150.04   $150.05   $150.00  
  Purchase #4 $224.88   3.650%   $233.0881   $233.09   $233.10   $233.10  
  Purchase #5 $149.91   8.166%   $162.1517   $162.15   $162.15   $162.20  
  Purchase #6 $33.55   5.442%   $35.3758   $35.38   $35.40   $35.40  
  Purchase #7 $15.73   6.533%   $16.7576   $16.76   $16.75   $16.80  
  7 purchase totals = $912.21       $966.7955   $966.80   $966.85   $966.90