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 $69.88   4.832%   $73.2566   $73.26   $73.25   $73.30  
  Purchase #2 $91.29   5.106%   $95.9513   $95.95   $95.95   $96.00  
  Purchase #3 $92.74   11.665%   $103.5581   $103.56   $103.55   $103.60  
  Purchase #4 $179.56   5.699%   $189.7931   $189.79   $189.80   $189.80  
  Purchase #5 $97.36   10.424%   $107.5088   $107.51   $107.50   $107.50  
  Purchase #6 $195.30   10.719%   $216.2342   $216.23   $216.25   $216.20  
  Purchase #7 $249.56   4.361%   $260.4433   $260.44   $260.45   $260.40  
  7 purchase totals = $975.69       $1,046.7454   $1,046.74   $1,046.75   $1,046.80