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 $93.73   8.545%   $101.7392   $101.74   $101.75   $101.70  
  Purchase #2 $215.81   5.454%   $227.5803   $227.58   $227.60   $227.60  
  Purchase #3 $98.71   3.112%   $101.7819   $101.78   $101.80   $101.80  
  Purchase #4 $246.79   6.287%   $262.3057   $262.31   $262.30   $262.30  
  Purchase #5 $191.80   6.293%   $203.87   $203.87   $203.85   $203.90  
  Purchase #6 $136.80   6.104%   $145.1503   $145.15   $145.15   $145.20  
  Purchase #7 $245.51   3.825%   $254.9008   $254.90   $254.90   $254.90  
  7 purchase totals = $1,229.15       $1,297.3282   $1,297.33   $1,297.35   $1,297.40