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 $66.54   11.139%   $73.9519   $73.95   $73.95   $74.00  
  Purchase #2 $32.75   6.784%   $34.9718   $34.97   $34.95   $35.00  
  Purchase #3 $242.38   5.266%   $255.1437   $255.14   $255.15   $255.10  
  Purchase #4 $175.44   9.378%   $191.8928   $191.89   $191.90   $191.90  
  Purchase #5 $177.28   4.189%   $184.7063   $184.71   $184.70   $184.70  
  Purchase #6 $225.95   9.385%   $247.1554   $247.16   $247.15   $247.20  
  Purchase #7 $236.80   3.437%   $244.9388   $244.94   $244.95   $244.90  
  7 purchase totals = $1,157.14       $1,232.7607   $1,232.76   $1,232.75   $1,232.80