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 $213.65   9.855%   $234.7052   $234.71   $234.70   $234.70  
  Purchase #2 $115.51   3.431%   $119.4731   $119.47   $119.45   $119.50  
  Purchase #3 $120.55   6.469%   $128.3484   $128.35   $128.35   $128.30  
  Purchase #4 $176.82   4.704%   $185.1376   $185.14   $185.15   $185.10  
  Purchase #5 $127.60   3.602%   $132.1962   $132.20   $132.20   $132.20  
  Purchase #6 $42.50   7.418%   $45.6527   $45.65   $45.65   $45.70  
  Purchase #7 $155.29   8.592%   $168.6325   $168.63   $168.65   $168.60  
  7 purchase totals = $951.92       $1,014.1457   $1,014.15   $1,014.15   $1,014.10