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 $140.48   8.681%   $152.6751   $152.68   $152.70   $152.70  
  Purchase #2 $240.50   10.407%   $265.5288   $265.53   $265.55   $265.50  
  Purchase #3 $149.41   11.699%   $166.8895   $166.89   $166.90   $166.90  
  Purchase #4 $236.56   3.385%   $244.5676   $244.57   $244.55   $244.60  
  Purchase #5 $7.32   4.272%   $7.6327   $7.63   $7.65   $7.60  
  Purchase #6 $134.71   12.773%   $151.9165   $151.92   $151.90   $151.90  
  Purchase #7 $205.70   6.452%   $218.9718   $218.97   $218.95   $219.00  
  7 purchase totals = $1,114.68       $1,208.1820   $1,208.19   $1,208.20   $1,208.20