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 $163.78   11.348%   $182.3658   $182.37   $182.35   $182.40  
  Purchase #2 $220.56   10.112%   $242.863   $242.86   $242.85   $242.90  
  Purchase #3 $94.54   12.749%   $106.5929   $106.59   $106.60   $106.60  
  Purchase #4 $192.65   3.376%   $199.1539   $199.15   $199.15   $199.20  
  Purchase #5 $185.66   9.658%   $203.591   $203.59   $203.60   $203.60  
  Purchase #6 $60.90   9.581%   $66.7348   $66.73   $66.75   $66.70  
  Purchase #7 $157.57   5.563%   $166.3356   $166.34   $166.35   $166.30  
  7 purchase totals = $1,075.66       $1,167.6370   $1,167.63   $1,167.65   $1,167.70