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 $53.96   9.864%   $59.2826   $59.28   $59.30   $59.30  
  Purchase #2 $55.36   8.736%   $60.1962   $60.20   $60.20   $60.20  
  Purchase #3 $195.34   12.436%   $219.6325   $219.63   $219.65   $219.60  
  Purchase #4 $245.94   11.105%   $273.2516   $273.25   $273.25   $273.30  
  Purchase #5 $177.57   6.815%   $189.6714   $189.67   $189.65   $189.70  
  Purchase #6 $119.66   10.859%   $132.6539   $132.65   $132.65   $132.70  
  Purchase #7 $169.69   9.357%   $185.5679   $185.57   $185.55   $185.60  
  7 purchase totals = $1,017.52       $1,120.2561   $1,120.25   $1,120.25   $1,120.40