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 $239.36   9.473%   $262.0346   $262.03   $262.05   $262.00  
  Purchase #2 $109.75   9.214%   $119.8624   $119.86   $119.85   $119.90  
  Purchase #3 $60.28   10.728%   $66.7468   $66.75   $66.75   $66.70  
  Purchase #4 $217.51   7.763%   $234.3953   $234.40   $234.40   $234.40  
  Purchase #5 $52.80   6.847%   $56.4152   $56.42   $56.40   $56.40  
  Purchase #6 $211.30   3.744%   $219.2111   $219.21   $219.20   $219.20  
  Purchase #7 $204.63   5.334%   $215.545   $215.55   $215.55   $215.50  
  7 purchase totals = $1,095.63       $1,174.2104   $1,174.22   $1,174.20   $1,174.10