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 $119.88   5.806%   $126.8402   $126.84   $126.85   $126.80  
  Purchase #2 $203.47   12.224%   $228.3422   $228.34   $228.35   $228.30  
  Purchase #3 $242.72   5.256%   $255.4774   $255.48   $255.50   $255.50  
  Purchase #4 $55.72   3.785%   $57.829   $57.83   $57.85   $57.80  
  Purchase #5 $71.83   5.361%   $75.6808   $75.68   $75.70   $75.70  
  Purchase #6 $210.47   5.533%   $222.1153   $222.12   $222.10   $222.10  
  Purchase #7 $191.89   9.377%   $209.8835   $209.88   $209.90   $209.90  
  7 purchase totals = $1,095.98       $1,176.1684   $1,176.17   $1,176.25   $1,176.10