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 $91.93   5.684%   $97.1553   $97.16   $97.15   $97.20  
  Purchase #2 $61.55   8.120%   $66.5479   $66.55   $66.55   $66.50  
  Purchase #3 $51.81   8.667%   $56.3004   $56.30   $56.30   $56.30  
  Purchase #4 $59.39   10.726%   $65.7602   $65.76   $65.75   $65.80  
  Purchase #5 $17.31   8.835%   $18.8393   $18.84   $18.85   $18.80  
  Purchase #6 $234.37   3.617%   $242.8472   $242.85   $242.85   $242.80  
  Purchase #7 $194.81   5.143%   $204.8291   $204.83   $204.85   $204.80  
  7 purchase totals = $711.17       $752.2794   $752.29   $752.30   $752.20