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 $228.91   5.468%   $241.4268   $241.43   $241.45   $241.40  
  Purchase #2 $92.30   13.447%   $104.7116   $104.71   $104.70   $104.70  
  Purchase #3 $39.33   12.638%   $44.3005   $44.30   $44.30   $44.30  
  Purchase #4 $201.29   13.676%   $228.8184   $228.82   $228.80   $228.80  
  Purchase #5 $126.76   4.278%   $132.1828   $132.18   $132.20   $132.20  
  Purchase #6 $182.47   6.161%   $193.712   $193.71   $193.70   $193.70  
  Purchase #7 $235.70   11.117%   $261.9028   $261.90   $261.90   $261.90  
  7 purchase totals = $1,106.76       $1,207.0549   $1,207.05   $1,207.05   $1,207.00