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 $113.73   4.800%   $119.189   $119.19   $119.20   $119.20  
  Purchase #2 $55.62   8.513%   $60.3549   $60.35   $60.35   $60.40  
  Purchase #3 $22.32   13.348%   $25.2993   $25.30   $25.30   $25.30  
  Purchase #4 $52.29   5.285%   $55.0535   $55.05   $55.05   $55.10  
  Purchase #5 $113.81   3.398%   $117.6773   $117.68   $117.70   $117.70  
  Purchase #6 $165.64   6.741%   $176.8058   $176.81   $176.80   $176.80  
  Purchase #7 $204.75   13.503%   $232.3974   $232.40   $232.40   $232.40  
  7 purchase totals = $728.16       $786.7772   $786.78   $786.80   $786.90