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 $222.62   9.279%   $243.2769   $243.28   $243.30   $243.30  
  Purchase #2 $55.73   4.519%   $58.2484   $58.25   $58.25   $58.20  
  Purchase #3 $216.74   3.761%   $224.8916   $224.89   $224.90   $224.90  
  Purchase #4 $131.41   13.796%   $149.5393   $149.54   $149.55   $149.50  
  Purchase #5 $115.97   8.433%   $125.7498   $125.75   $125.75   $125.70  
  Purchase #6 $128.43   6.858%   $137.2377   $137.24   $137.25   $137.20  
  Purchase #7 $112.31   10.634%   $124.253   $124.25   $124.25   $124.30  
  7 purchase totals = $983.21       $1,063.1967   $1,063.20   $1,063.25   $1,063.10