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 $91.61   4.242%   $95.4961   $95.50   $95.50   $95.50  
  Purchase #2 $100.81   6.825%   $107.6903   $107.69   $107.70   $107.70  
  Purchase #3 $165.51   13.215%   $187.3821   $187.38   $187.40   $187.40  
  Purchase #4 $134.38   13.442%   $152.4434   $152.44   $152.45   $152.40  
  Purchase #5 $120.99   9.700%   $132.726   $132.73   $132.75   $132.70  
  Purchase #6 $228.67   11.108%   $254.0707   $254.07   $254.05   $254.10  
  Purchase #7 $103.49   11.147%   $115.026   $115.03   $115.05   $115.00  
  7 purchase totals = $945.46       $1,044.8346   $1,044.84   $1,044.90   $1,044.80