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 $110.60   7.575%   $118.978   $118.98   $119.00   $119.00  
  Purchase #2 $249.66   6.363%   $265.5459   $265.55   $265.55   $265.50  
  Purchase #3 $51.27   6.224%   $54.461   $54.46   $54.45   $54.50  
  Purchase #4 $164.26   5.459%   $173.227   $173.23   $173.25   $173.20  
  Purchase #5 $94.66   3.533%   $98.0043   $98.00   $98.00   $98.00  
  Purchase #6 $69.49   7.858%   $74.9505   $74.95   $74.95   $75.00  
  Purchase #7 $60.74   5.720%   $64.2143   $64.21   $64.20   $64.20  
  7 purchase totals = $800.68       $849.3810   $849.38   $849.40   $849.40