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 $94.63   4.462%   $98.8524   $98.85   $98.85   $98.90  
  Purchase #2 $171.65   4.176%   $178.8181   $178.82   $178.80   $178.80  
  Purchase #3 $190.34   12.599%   $214.3209   $214.32   $214.30   $214.30  
  Purchase #4 $55.64   10.115%   $61.268   $61.27   $61.25   $61.30  
  Purchase #5 $195.85   11.462%   $218.2983   $218.30   $218.30   $218.30  
  Purchase #6 $60.37   7.164%   $64.6949   $64.69   $64.70   $64.70  
  Purchase #7 $100.93   12.757%   $113.8056   $113.81   $113.80   $113.80  
  7 purchase totals = $869.41       $950.0582   $950.06   $950.00   $950.10