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 $84.60   12.130%   $94.862   $94.86   $94.85   $94.90  
  Purchase #2 $59.30   9.742%   $65.077   $65.08   $65.10   $65.10  
  Purchase #3 $226.83   8.435%   $245.9631   $245.96   $245.95   $246.00  
  Purchase #4 $161.82   4.518%   $169.131   $169.13   $169.15   $169.10  
  Purchase #5 $21.50   6.782%   $22.9581   $22.96   $22.95   $23.00  
  Purchase #6 $46.83   4.532%   $48.9523   $48.95   $48.95   $49.00  
  Purchase #7 $158.55   11.689%   $177.0829   $177.08   $177.10   $177.10  
  7 purchase totals = $759.43       $824.0264   $824.02   $824.05   $824.20