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 $92.51   3.589%   $95.8302   $95.83   $95.85   $95.80  
  Purchase #2 $195.53   5.230%   $205.7562   $205.76   $205.75   $205.80  
  Purchase #3 $226.25   9.275%   $247.2347   $247.23   $247.25   $247.20  
  Purchase #4 $90.98   5.191%   $95.7028   $95.70   $95.70   $95.70  
  Purchase #5 $226.52   13.346%   $256.7514   $256.75   $256.75   $256.80  
  Purchase #6 $53.98   5.862%   $57.1443   $57.14   $57.15   $57.10  
  Purchase #7 $185.49   4.812%   $194.4158   $194.42   $194.40   $194.40  
  7 purchase totals = $1,071.26       $1,152.8354   $1,152.83   $1,152.85   $1,152.80