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 $41.73   10.180%   $45.9781   $45.98   $46.00   $46.00  
  Purchase #2 $181.97   7.354%   $195.3521   $195.35   $195.35   $195.40  
  Purchase #3 $118.46   11.200%   $131.7275   $131.73   $131.75   $131.70  
  Purchase #4 $216.34   13.738%   $246.0608   $246.06   $246.05   $246.10  
  Purchase #5 $67.86   13.172%   $76.7985   $76.80   $76.80   $76.80  
  Purchase #6 $54.37   7.704%   $58.5587   $58.56   $58.55   $58.60  
  Purchase #7 $194.29   7.778%   $209.4019   $209.40   $209.40   $209.40  
  7 purchase totals = $875.02       $963.8776   $963.88   $963.90   $964.00