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 $200.73   6.711%   $214.201   $214.20   $214.20   $214.20  
  Purchase #2 $8.69   9.632%   $9.527   $9.53   $9.55   $9.50  
  Purchase #3 $61.85   5.859%   $65.4738   $65.47   $65.45   $65.50  
  Purchase #4 $217.83   13.485%   $247.2044   $247.20   $247.20   $247.20  
  Purchase #5 $63.33   11.727%   $70.7567   $70.76   $70.75   $70.80  
  Purchase #6 $161.34   4.183%   $168.0889   $168.09   $168.10   $168.10  
  Purchase #7 $166.34   13.130%   $188.1804   $188.18   $188.20   $188.20  
  7 purchase totals = $880.11       $963.4322   $963.43   $963.45   $963.50