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 $69.85   4.865%   $73.2482   $73.25   $73.25   $73.20  
  Purchase #2 $192.87   11.548%   $215.1426   $215.14   $215.15   $215.10  
  Purchase #3 $116.42   5.281%   $122.5681   $122.57   $122.55   $122.60  
  Purchase #4 $200.87   7.474%   $215.883   $215.88   $215.90   $215.90  
  Purchase #5 $102.91   13.452%   $116.7535   $116.75   $116.75   $116.80  
  Purchase #6 $48.97   12.822%   $55.2489   $55.25   $55.25   $55.20  
  Purchase #7 $242.65   8.698%   $263.7557   $263.76   $263.75   $263.80  
  7 purchase totals = $974.54       $1,062.6000   $1,062.60   $1,062.60   $1,062.60