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 $204.58   4.709%   $214.2137   $214.21   $214.20   $214.20  
  Purchase #2 $162.34   3.295%   $167.6891   $167.69   $167.70   $167.70  
  Purchase #3 $160.78   4.715%   $168.3608   $168.36   $168.35   $168.40  
  Purchase #4 $99.92   10.487%   $110.3986   $110.40   $110.40   $110.40  
  Purchase #5 $15.26   8.844%   $16.6096   $16.61   $16.60   $16.60  
  Purchase #6 $199.64   4.129%   $207.8831   $207.88   $207.90   $207.90  
  Purchase #7 $221.37   5.771%   $234.1453   $234.15   $234.15   $234.10  
  7 purchase totals = $1,063.89       $1,119.3002   $1,119.30   $1,119.30   $1,119.30