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 $108.63   5.784%   $114.9132   $114.91   $114.90   $114.90  
  Purchase #2 $130.38   13.364%   $147.804   $147.80   $147.80   $147.80  
  Purchase #3 $58.98   5.709%   $62.3472   $62.35   $62.35   $62.30  
  Purchase #4 $115.74   4.713%   $121.1948   $121.19   $121.20   $121.20  
  Purchase #5 $179.37   5.124%   $188.5609   $188.56   $188.55   $188.60  
  Purchase #6 $180.59   9.742%   $198.1831   $198.18   $198.20   $198.20  
  Purchase #7 $202.34   5.569%   $213.6083   $213.61   $213.60   $213.60  
  7 purchase totals = $976.03       $1,046.6115   $1,046.60   $1,046.60   $1,046.60