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 $91.89   3.231%   $94.859   $94.86   $94.85   $94.90  
  Purchase #2 $122.96   5.592%   $129.8359   $129.84   $129.85   $129.80  
  Purchase #3 $61.60   7.793%   $66.4005   $66.40   $66.40   $66.40  
  Purchase #4 $221.75   6.546%   $236.2658   $236.27   $236.25   $236.30  
  Purchase #5 $116.72   7.684%   $125.6888   $125.69   $125.70   $125.70  
  Purchase #6 $93.33   5.748%   $98.6946   $98.69   $98.70   $98.70  
  Purchase #7 $193.61   5.396%   $204.0572   $204.06   $204.05   $204.10  
  7 purchase totals = $901.86       $955.8018   $955.81   $955.80   $955.90