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 $227.83   8.252%   $246.6305   $246.63   $246.65   $246.60  
  Purchase #2 $58.97   6.388%   $62.737   $62.74   $62.75   $62.70  
  Purchase #3 $120.95   3.449%   $125.1216   $125.12   $125.10   $125.10  
  Purchase #4 $49.32   9.518%   $54.0143   $54.01   $54.00   $54.00  
  Purchase #5 $50.67   9.328%   $55.3965   $55.40   $55.40   $55.40  
  Purchase #6 $89.30   5.282%   $94.0168   $94.02   $94.00   $94.00  
  Purchase #7 $101.42   12.492%   $114.0894   $114.09   $114.10   $114.10  
  7 purchase totals = $698.46       $752.0061   $752.01   $752.00   $751.90