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 $204.35   10.733%   $226.2829   $226.28   $226.30   $226.30  
  Purchase #2 $146.99   8.431%   $159.3827   $159.38   $159.40   $159.40  
  Purchase #3 $117.46   11.269%   $130.6966   $130.70   $130.70   $130.70  
  Purchase #4 $183.58   9.277%   $200.6107   $200.61   $200.60   $200.60  
  Purchase #5 $91.59   13.855%   $104.2798   $104.28   $104.30   $104.30  
  Purchase #6 $208.73   4.636%   $218.4067   $218.41   $218.40   $218.40  
  Purchase #7 $148.69   4.588%   $155.5119   $155.51   $155.50   $155.50  
  7 purchase totals = $1,101.39       $1,195.1713   $1,195.17   $1,195.20   $1,195.20