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 $106.68   11.696%   $119.1573   $119.16   $119.15   $119.20  
  Purchase #2 $189.60   4.391%   $197.9253   $197.93   $197.95   $197.90  
  Purchase #3 $46.26   13.687%   $52.5916   $52.59   $52.60   $52.60  
  Purchase #4 $99.98   5.121%   $105.1   $105.10   $105.10   $105.10  
  Purchase #5 $140.83   9.327%   $153.9652   $153.97   $153.95   $154.00  
  Purchase #6 $249.40   10.696%   $276.0758   $276.08   $276.10   $276.10  
  Purchase #7 $35.44   3.836%   $36.7995   $36.80   $36.80   $36.80  
  7 purchase totals = $868.19       $941.6147   $941.63   $941.65   $941.70