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 $49.63   8.751%   $53.9731   $53.97   $53.95   $54.00  
  Purchase #2 $150.88   11.329%   $167.9732   $167.97   $167.95   $168.00  
  Purchase #3 $149.64   10.105%   $164.7611   $164.76   $164.75   $164.80  
  Purchase #4 $168.40   6.211%   $178.8593   $178.86   $178.85   $178.90  
  Purchase #5 $192.82   12.161%   $216.2688   $216.27   $216.25   $216.30  
  Purchase #6 $204.91   13.707%   $232.997   $233.00   $233.00   $233.00  
  Purchase #7 $180.67   4.165%   $188.1949   $188.19   $188.20   $188.20  
  7 purchase totals = $1,096.95       $1,203.0274   $1,203.02   $1,202.95   $1,203.20