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 $125.76   5.443%   $132.6051   $132.61   $132.60   $132.60  
  Purchase #2 $211.60   6.154%   $224.6219   $224.62   $224.60   $224.60  
  Purchase #3 $25.34   5.617%   $26.7633   $26.76   $26.75   $26.80  
  Purchase #4 $245.64   7.360%   $263.7191   $263.72   $263.70   $263.70  
  Purchase #5 $97.55   3.573%   $101.0355   $101.04   $101.05   $101.00  
  Purchase #6 $155.94   9.467%   $170.7028   $170.70   $170.70   $170.70  
  Purchase #7 $224.26   4.491%   $234.3315   $234.33   $234.35   $234.30  
  7 purchase totals = $1,086.09       $1,153.7792   $1,153.78   $1,153.75   $1,153.70