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 $88.50   9.329%   $96.7562   $96.76   $96.75   $96.80  
  Purchase #2 $214.98   5.134%   $226.0171   $226.02   $226.00   $226.00  
  Purchase #3 $130.35   3.340%   $134.7037   $134.70   $134.70   $134.70  
  Purchase #4 $159.74   4.552%   $167.0114   $167.01   $167.00   $167.00  
  Purchase #5 $57.25   9.422%   $62.6441   $62.64   $62.65   $62.60  
  Purchase #6 $146.85   3.780%   $152.4009   $152.40   $152.40   $152.40  
  Purchase #7 $209.32   3.164%   $215.9429   $215.94   $215.95   $215.90  
  7 purchase totals = $1,006.99       $1,055.4763   $1,055.47   $1,055.45   $1,055.40