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 $213.97   4.826%   $224.2962   $224.30   $224.30   $224.30  
  Purchase #2 $81.74   11.668%   $91.2774   $91.28   $91.30   $91.30  
  Purchase #3 $68.37   4.432%   $71.4002   $71.40   $71.40   $71.40  
  Purchase #4 $153.36   13.195%   $173.5959   $173.60   $173.60   $173.60  
  Purchase #5 $79.32   6.678%   $84.617   $84.62   $84.60   $84.60  
  Purchase #6 $53.37   8.383%   $57.844   $57.84   $57.85   $57.80  
  Purchase #7 $10.62   7.649%   $11.4323   $11.43   $11.45   $11.40  
  7 purchase totals = $660.75       $714.4630   $714.47   $714.50   $714.40