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 $67.76   4.378%   $70.7265   $70.73   $70.75   $70.70  
  Purchase #2 $235.29   10.614%   $260.2637   $260.26   $260.25   $260.30  
  Purchase #3 $193.74   8.209%   $209.6441   $209.64   $209.65   $209.60  
  Purchase #4 $122.56   12.851%   $138.3102   $138.31   $138.30   $138.30  
  Purchase #5 $234.58   4.133%   $244.2752   $244.28   $244.30   $244.30  
  Purchase #6 $203.56   5.248%   $214.2428   $214.24   $214.25   $214.20  
  Purchase #7 $201.38   11.306%   $224.148   $224.15   $224.15   $224.10  
  7 purchase totals = $1,258.87       $1,361.6105   $1,361.61   $1,361.65   $1,361.50