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 $194.29   11.449%   $216.5343   $216.53   $216.55   $216.50  
  Purchase #2 $146.43   3.859%   $152.0807   $152.08   $152.10   $152.10  
  Purchase #3 $76.47   9.754%   $83.9289   $83.93   $83.95   $83.90  
  Purchase #4 $85.97   10.455%   $94.9582   $94.96   $94.95   $95.00  
  Purchase #5 $86.44   5.800%   $91.4535   $91.45   $91.45   $91.50  
  Purchase #6 $229.49   6.323%   $244.0007   $244.00   $244.00   $244.00  
  Purchase #7 $143.62   13.715%   $163.3175   $163.32   $163.30   $163.30  
  7 purchase totals = $962.71       $1,046.2738   $1,046.27   $1,046.30   $1,046.30