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 $68.69   11.474%   $76.5715   $76.57   $76.55   $76.60  
  Purchase #2 $185.40   11.105%   $205.9887   $205.99   $206.00   $206.00  
  Purchase #3 $248.46   4.862%   $260.5401   $260.54   $260.55   $260.50  
  Purchase #4 $196.81   11.152%   $218.7583   $218.76   $218.75   $218.80  
  Purchase #5 $84.86   12.534%   $95.4964   $95.50   $95.50   $95.50  
  Purchase #6 $115.96   3.651%   $120.1937   $120.19   $120.20   $120.20  
  Purchase #7 $94.68   13.457%   $107.4211   $107.42   $107.40   $107.40  
  7 purchase totals = $994.86       $1,084.9698   $1,084.97   $1,084.95   $1,085.00