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 $84.36   13.607%   $95.8389   $95.84   $95.85   $95.80  
  Purchase #2 $230.73   9.304%   $252.1971   $252.20   $252.20   $252.20  
  Purchase #3 $153.79   7.734%   $165.6841   $165.68   $165.70   $165.70  
  Purchase #4 $212.60   13.622%   $241.5604   $241.56   $241.55   $241.60  
  Purchase #5 $234.86   11.455%   $261.7632   $261.76   $261.75   $261.80  
  Purchase #6 $102.94   11.432%   $114.7081   $114.71   $114.70   $114.70  
  Purchase #7 $106.52   3.649%   $110.4069   $110.41   $110.40   $110.40  
  7 purchase totals = $1,125.80       $1,242.1587   $1,242.16   $1,242.15   $1,242.20