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 $86.60   5.682%   $91.5206   $91.52   $91.50   $91.50  
  Purchase #2 $187.77   3.480%   $194.3044   $194.30   $194.30   $194.30  
  Purchase #3 $180.97   11.277%   $201.378   $201.38   $201.40   $201.40  
  Purchase #4 $106.73   5.333%   $112.4219   $112.42   $112.40   $112.40  
  Purchase #5 $143.67   10.181%   $158.297   $158.30   $158.30   $158.30  
  Purchase #6 $81.88   7.497%   $88.0185   $88.02   $88.00   $88.00  
  Purchase #7 $167.66   11.152%   $186.3574   $186.36   $186.35   $186.40  
  7 purchase totals = $955.28       $1,032.2978   $1,032.30   $1,032.25   $1,032.30