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 $214.44   4.508%   $224.107   $224.11   $224.10   $224.10  
  Purchase #2 $245.38   7.264%   $263.2044   $263.20   $263.20   $263.20  
  Purchase #3 $52.36   9.322%   $57.241   $57.24   $57.25   $57.20  
  Purchase #4 $224.82   6.132%   $238.606   $238.61   $238.60   $238.60  
  Purchase #5 $172.78   5.788%   $182.7805   $182.78   $182.80   $182.80  
  Purchase #6 $92.85   5.843%   $98.2752   $98.28   $98.30   $98.30  
  Purchase #7 $125.84   8.823%   $136.9429   $136.94   $136.95   $136.90  
  7 purchase totals = $1,128.47       $1,201.1570   $1,201.16   $1,201.20   $1,201.10