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 $60.28   4.441%   $62.957   $62.96   $62.95   $63.00  
  Purchase #2 $114.94   9.166%   $125.4754   $125.48   $125.50   $125.50  
  Purchase #3 $95.88   12.234%   $107.61   $107.61   $107.60   $107.60  
  Purchase #4 $53.72   9.450%   $58.7965   $58.80   $58.80   $58.80  
  Purchase #5 $50.42   8.350%   $54.6301   $54.63   $54.65   $54.60  
  Purchase #6 $36.93   3.148%   $38.0926   $38.09   $38.10   $38.10  
  Purchase #7 $44.58   3.732%   $46.2437   $46.24   $46.25   $46.20  
  7 purchase totals = $456.75       $493.8053   $493.81   $493.85   $493.80