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 $163.59   11.364%   $182.1804   $182.18   $182.20   $182.20  
  Purchase #2 $150.40   5.838%   $159.1804   $159.18   $159.20   $159.20  
  Purchase #3 $227.40   6.255%   $241.6239   $241.62   $241.60   $241.60  
  Purchase #4 $53.74   13.873%   $61.1954   $61.20   $61.20   $61.20  
  Purchase #5 $32.78   4.105%   $34.1256   $34.13   $34.15   $34.10  
  Purchase #6 $158.36   5.504%   $167.0761   $167.08   $167.10   $167.10  
  Purchase #7 $188.90   11.267%   $210.1834   $210.18   $210.20   $210.20  
  7 purchase totals = $975.17       $1,055.5652   $1,055.57   $1,055.65   $1,055.60