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 $83.45   13.302%   $94.5505   $94.55   $94.55   $94.60  
  Purchase #2 $166.39   3.161%   $171.6496   $171.65   $171.65   $171.60  
  Purchase #3 $49.59   12.170%   $55.6251   $55.63   $55.65   $55.60  
  Purchase #4 $196.62   6.745%   $209.882   $209.88   $209.90   $209.90  
  Purchase #5 $132.81   5.135%   $139.6298   $139.63   $139.65   $139.60  
  Purchase #6 $18.52   6.705%   $19.7618   $19.76   $19.75   $19.80  
  Purchase #7 $244.27   5.673%   $258.1274   $258.13   $258.15   $258.10  
  7 purchase totals = $891.65       $949.2262   $949.23   $949.30   $949.20