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 $176.78   10.310%   $195.006   $195.01   $195.00   $195.00  
  Purchase #2 $86.59   11.232%   $96.3158   $96.32   $96.30   $96.30  
  Purchase #3 $135.28   8.503%   $146.7829   $146.78   $146.80   $146.80  
  Purchase #4 $169.91   10.339%   $187.477   $187.48   $187.50   $187.50  
  Purchase #5 $102.49   13.291%   $116.1119   $116.11   $116.10   $116.10  
  Purchase #6 $123.65   6.338%   $131.4869   $131.49   $131.50   $131.50  
  Purchase #7 $67.71   13.371%   $76.7635   $76.76   $76.75   $76.80  
  7 purchase totals = $862.41       $949.9440   $949.95   $949.95   $950.00