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 $32.84   5.197%   $34.5467   $34.55   $34.55   $34.50  
  Purchase #2 $223.33   5.785%   $236.2496   $236.25   $236.25   $236.20  
  Purchase #3 $43.79   11.680%   $48.9047   $48.90   $48.90   $48.90  
  Purchase #4 $72.43   5.187%   $76.1869   $76.19   $76.20   $76.20  
  Purchase #5 $123.29   5.675%   $130.2867   $130.29   $130.30   $130.30  
  Purchase #6 $121.40   4.481%   $126.8399   $126.84   $126.85   $126.80  
  Purchase #7 $231.63   4.490%   $242.0302   $242.03   $242.05   $242.00  
  7 purchase totals = $848.71       $895.0447   $895.05   $895.10   $894.90