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 $58.65   6.518%   $62.4728   $62.47   $62.45   $62.50  
  Purchase #2 $208.76   4.510%   $218.1751   $218.18   $218.20   $218.20  
  Purchase #3 $158.54   10.521%   $175.22   $175.22   $175.20   $175.20  
  Purchase #4 $238.93   9.219%   $260.957   $260.96   $260.95   $261.00  
  Purchase #5 $237.31   10.321%   $261.8028   $261.80   $261.80   $261.80  
  Purchase #6 $167.31   11.794%   $187.0425   $187.04   $187.05   $187.00  
  Purchase #7 $31.76   9.123%   $34.6575   $34.66   $34.65   $34.70  
  7 purchase totals = $1,101.26       $1,200.3277   $1,200.33   $1,200.30   $1,200.40