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 $213.40   7.425%   $229.245   $229.25   $229.25   $229.20  
  Purchase #2 $61.36   11.749%   $68.5692   $68.57   $68.55   $68.60  
  Purchase #3 $219.91   13.254%   $249.0569   $249.06   $249.05   $249.10  
  Purchase #4 $71.79   13.680%   $81.6109   $81.61   $81.60   $81.60  
  Purchase #5 $94.69   7.476%   $101.769   $101.77   $101.75   $101.80  
  Purchase #6 $77.86   4.196%   $81.127   $81.13   $81.15   $81.10  
  Purchase #7 $209.69   7.727%   $225.8927   $225.89   $225.90   $225.90  
  7 purchase totals = $948.70       $1,037.2707   $1,037.28   $1,037.25   $1,037.30