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 $51.41   4.752%   $53.853   $53.85   $53.85   $53.90  
  Purchase #2 $146.79   10.282%   $161.8829   $161.88   $161.90   $161.90  
  Purchase #3 $149.67   11.578%   $166.9988   $167.00   $167.00   $167.00  
  Purchase #4 $202.56   5.775%   $214.2578   $214.26   $214.25   $214.30  
  Purchase #5 $232.46   7.556%   $250.0247   $250.02   $250.00   $250.00  
  Purchase #6 $27.54   7.375%   $29.5711   $29.57   $29.55   $29.60  
  Purchase #7 $53.82   5.675%   $56.8743   $56.87   $56.85   $56.90  
  7 purchase totals = $864.25       $933.4626   $933.45   $933.40   $933.60