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 $192.88   7.582%   $207.5042   $207.50   $207.50   $207.50  
  Purchase #2 $189.53   3.394%   $195.9626   $195.96   $195.95   $196.00  
  Purchase #3 $154.57   6.133%   $164.0498   $164.05   $164.05   $164.00  
  Purchase #4 $35.89   3.512%   $37.1505   $37.15   $37.15   $37.20  
  Purchase #5 $222.99   6.507%   $237.5   $237.50   $237.50   $237.50  
  Purchase #6 $148.63   5.761%   $157.1926   $157.19   $157.20   $157.20  
  Purchase #7 $211.81   7.861%   $228.4604   $228.46   $228.45   $228.50  
  7 purchase totals = $1,156.30       $1,227.8201   $1,227.81   $1,227.80   $1,227.90