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 $68.86   4.723%   $72.1123   $72.11   $72.10   $72.10  
  Purchase #2 $92.43   3.784%   $95.9276   $95.93   $95.95   $95.90  
  Purchase #3 $124.31   9.605%   $136.25   $136.25   $136.25   $136.30  
  Purchase #4 $197.35   10.435%   $217.9435   $217.94   $217.95   $217.90  
  Purchase #5 $249.94   9.774%   $274.3691   $274.37   $274.35   $274.40  
  Purchase #6 $32.97   5.602%   $34.817   $34.82   $34.80   $34.80  
  Purchase #7 $185.94   10.629%   $205.7036   $205.70   $205.70   $205.70  
  7 purchase totals = $951.80       $1,037.1231   $1,037.12   $1,037.10   $1,037.10