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 $229.72   10.262%   $253.2939   $253.29   $253.30   $253.30  
  Purchase #2 $38.99   3.746%   $40.4506   $40.45   $40.45   $40.50  
  Purchase #3 $88.83   5.691%   $93.8853   $93.89   $93.90   $93.90  
  Purchase #4 $212.34   11.646%   $237.0691   $237.07   $237.05   $237.10  
  Purchase #5 $32.26   13.872%   $36.7351   $36.74   $36.75   $36.70  
  Purchase #6 $10.52   11.856%   $11.7673   $11.77   $11.75   $11.80  
  Purchase #7 $205.57   8.223%   $222.474   $222.47   $222.45   $222.50  
  7 purchase totals = $818.23       $895.6753   $895.68   $895.65   $895.80