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 $119.67   5.748%   $126.5486   $126.55   $126.55   $126.50  
  Purchase #2 $113.80   3.704%   $118.0152   $118.02   $118.00   $118.00  
  Purchase #3 $210.67   10.612%   $233.0263   $233.03   $233.05   $233.00  
  Purchase #4 $39.58   6.577%   $42.1832   $42.18   $42.20   $42.20  
  Purchase #5 $167.62   3.105%   $172.8246   $172.82   $172.80   $172.80  
  Purchase #6 $63.51   3.529%   $65.7513   $65.75   $65.75   $65.80  
  Purchase #7 $8.72   5.810%   $9.2266   $9.23   $9.25   $9.20  
  7 purchase totals = $723.57       $767.5758   $767.58   $767.60   $767.50