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 $180.33   8.453%   $195.5733   $195.57   $195.55   $195.60  
  Purchase #2 $215.91   5.461%   $227.7008   $227.70   $227.70   $227.70  
  Purchase #3 $182.64   7.200%   $195.7901   $195.79   $195.80   $195.80  
  Purchase #4 $105.76   8.519%   $114.7697   $114.77   $114.75   $114.80  
  Purchase #5 $117.91   12.383%   $132.5108   $132.51   $132.50   $132.50  
  Purchase #6 $187.79   4.829%   $196.8584   $196.86   $196.85   $196.90  
  Purchase #7 $8.92   11.110%   $9.911   $9.91   $9.90   $9.90  
  7 purchase totals = $999.26       $1,073.1141   $1,073.11   $1,073.05   $1,073.20