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 $62.37   11.814%   $69.7384   $69.74   $69.75   $69.70  
  Purchase #2 $212.68   11.507%   $237.1531   $237.15   $237.15   $237.20  
  Purchase #3 $156.94   10.750%   $173.8111   $173.81   $173.80   $173.80  
  Purchase #4 $146.25   5.517%   $154.3186   $154.32   $154.30   $154.30  
  Purchase #5 $209.92   10.128%   $231.1807   $231.18   $231.20   $231.20  
  Purchase #6 $181.74   12.428%   $204.3266   $204.33   $204.35   $204.30  
  Purchase #7 $185.25   6.707%   $197.6747   $197.67   $197.65   $197.70  
  7 purchase totals = $1,155.15       $1,268.2032   $1,268.20   $1,268.20   $1,268.20