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 $58.69   7.871%   $63.3095   $63.31   $63.30   $63.30  
  Purchase #2 $214.91   4.835%   $225.3009   $225.30   $225.30   $225.30  
  Purchase #3 $94.85   4.393%   $99.0168   $99.02   $99.00   $99.00  
  Purchase #4 $76.29   11.719%   $85.2304   $85.23   $85.25   $85.20  
  Purchase #5 $83.97   12.354%   $94.3437   $94.34   $94.35   $94.30  
  Purchase #6 $185.93   5.239%   $195.6709   $195.67   $195.65   $195.70  
  Purchase #7 $188.97   6.259%   $200.7976   $200.80   $200.80   $200.80  
  7 purchase totals = $903.61       $963.6698   $963.67   $963.65   $963.60