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 $216.42   13.723%   $246.1193   $246.12   $246.10   $246.10  
  Purchase #2 $86.51   13.400%   $98.1023   $98.10   $98.10   $98.10  
  Purchase #3 $178.86   5.480%   $188.6615   $188.66   $188.65   $188.70  
  Purchase #4 $226.70   5.191%   $238.468   $238.47   $238.45   $238.50  
  Purchase #5 $113.74   4.587%   $118.9573   $118.96   $118.95   $119.00  
  Purchase #6 $53.36   12.426%   $59.9905   $59.99   $60.00   $60.00  
  Purchase #7 $232.57   8.105%   $251.4198   $251.42   $251.40   $251.40  
  7 purchase totals = $1,108.16       $1,201.7187   $1,201.72   $1,201.65   $1,201.80