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 $24.46   4.721%   $25.6148   $25.61   $25.60   $25.60  
  Purchase #2 $95.57   11.311%   $106.3799   $106.38   $106.40   $106.40  
  Purchase #3 $105.79   9.840%   $116.1997   $116.20   $116.20   $116.20  
  Purchase #4 $70.72   7.751%   $76.2015   $76.20   $76.20   $76.20  
  Purchase #5 $133.98   8.630%   $145.5425   $145.54   $145.55   $145.50  
  Purchase #6 $112.76   10.501%   $124.6009   $124.60   $124.60   $124.60  
  Purchase #7 $115.98   3.685%   $120.2539   $120.25   $120.25   $120.30  
  7 purchase totals = $659.26       $714.7932   $714.78   $714.80   $714.80