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 $216.81   11.390%   $241.5047   $241.50   $241.50   $241.50  
  Purchase #2 $200.25   10.553%   $221.3824   $221.38   $221.40   $221.40  
  Purchase #3 $170.51   6.862%   $182.2104   $182.21   $182.20   $182.20  
  Purchase #4 $243.72   9.233%   $266.2227   $266.22   $266.20   $266.20  
  Purchase #5 $181.85   6.411%   $193.5084   $193.51   $193.50   $193.50  
  Purchase #6 $86.31   8.793%   $93.8992   $93.90   $93.90   $93.90  
  Purchase #7 $245.97   7.817%   $265.1975   $265.20   $265.20   $265.20  
  7 purchase totals = $1,345.42       $1,463.9253   $1,463.92   $1,463.90   $1,463.90