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 $86.39   10.585%   $95.5344   $95.53   $95.55   $95.50  
  Purchase #2 $173.85   12.371%   $195.357   $195.36   $195.35   $195.40  
  Purchase #3 $233.74   9.303%   $255.4848   $255.48   $255.50   $255.50  
  Purchase #4 $249.75   9.423%   $273.2839   $273.28   $273.30   $273.30  
  Purchase #5 $9.59   5.769%   $10.1432   $10.14   $10.15   $10.10  
  Purchase #6 $218.87   6.514%   $233.1272   $233.13   $233.15   $233.10  
  Purchase #7 $245.80   11.182%   $273.2854   $273.29   $273.30   $273.30  
  7 purchase totals = $1,217.99       $1,336.2159   $1,336.21   $1,336.30   $1,336.20