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 $62.76   10.287%   $69.2161   $69.22   $69.20   $69.20  
  Purchase #2 $210.92   11.610%   $235.4078   $235.41   $235.40   $235.40  
  Purchase #3 $187.99   8.554%   $204.0707   $204.07   $204.05   $204.10  
  Purchase #4 $162.40   3.527%   $168.1278   $168.13   $168.15   $168.10  
  Purchase #5 $88.62   4.521%   $92.6265   $92.63   $92.65   $92.60  
  Purchase #6 $91.71   3.538%   $94.9547   $94.95   $94.95   $95.00  
  Purchase #7 $7.83   11.801%   $8.754   $8.75   $8.75   $8.80  
  7 purchase totals = $812.23       $873.1576   $873.16   $873.15   $873.20