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 $88.61   5.260%   $93.2709   $93.27   $93.25   $93.30  
  Purchase #2 $48.60   6.373%   $51.6973   $51.70   $51.70   $51.70  
  Purchase #3 $78.40   5.228%   $82.4988   $82.50   $82.50   $82.50  
  Purchase #4 $218.71   13.787%   $248.8635   $248.86   $248.85   $248.90  
  Purchase #5 $231.83   12.499%   $260.8064   $260.81   $260.80   $260.80  
  Purchase #6 $241.75   8.427%   $262.1223   $262.12   $262.10   $262.10  
  Purchase #7 $116.48   9.128%   $127.1123   $127.11   $127.10   $127.10  
  7 purchase totals = $1,024.38       $1,126.3715   $1,126.37   $1,126.30   $1,126.40