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 $44.26   6.467%   $47.1223   $47.12   $47.10   $47.10  
  Purchase #2 $136.98   10.693%   $151.6273   $151.63   $151.65   $151.60  
  Purchase #3 $43.64   3.440%   $45.1412   $45.14   $45.15   $45.10  
  Purchase #4 $214.99   4.428%   $224.5098   $224.51   $224.50   $224.50  
  Purchase #5 $21.57   11.334%   $24.0147   $24.01   $24.00   $24.00  
  Purchase #6 $132.62   10.760%   $146.8899   $146.89   $146.90   $146.90  
  Purchase #7 $137.57   13.303%   $155.8709   $155.87   $155.85   $155.90  
  7 purchase totals = $731.63       $795.1761   $795.17   $795.15   $795.10