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 $85.46   12.279%   $95.9536   $95.95   $95.95   $96.00  
  Purchase #2 $171.78   8.872%   $187.0203   $187.02   $187.00   $187.00  
  Purchase #3 $250.51   12.178%   $281.0171   $281.02   $281.00   $281.00  
  Purchase #4 $217.84   5.192%   $229.1503   $229.15   $229.15   $229.20  
  Purchase #5 $191.38   5.756%   $202.3958   $202.40   $202.40   $202.40  
  Purchase #6 $222.55   12.385%   $250.1128   $250.11   $250.10   $250.10  
  Purchase #7 $41.98   10.855%   $46.5369   $46.54   $46.55   $46.50  
  7 purchase totals = $1,181.50       $1,292.1868   $1,292.19   $1,292.15   $1,292.20