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 $60.93   3.664%   $63.1625   $63.16   $63.15   $63.20  
  Purchase #2 $233.78   3.812%   $242.6917   $242.69   $242.70   $242.70  
  Purchase #3 $32.64   7.775%   $35.1778   $35.18   $35.20   $35.20  
  Purchase #4 $244.97   13.535%   $278.1267   $278.13   $278.15   $278.10  
  Purchase #5 $86.65   9.148%   $94.5767   $94.58   $94.60   $94.60  
  Purchase #6 $144.86   13.815%   $164.8724   $164.87   $164.85   $164.90  
  Purchase #7 $206.29   12.465%   $232.004   $232.00   $232.00   $232.00  
  7 purchase totals = $1,010.12       $1,110.6118   $1,110.61   $1,110.65   $1,110.70