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 $213.92   6.535%   $227.8997   $227.90   $227.90   $227.90  
  Purchase #2 $193.63   4.554%   $202.4479   $202.45   $202.45   $202.40  
  Purchase #3 $208.84   10.873%   $231.5472   $231.55   $231.55   $231.50  
  Purchase #4 $183.77   4.761%   $192.5193   $192.52   $192.50   $192.50  
  Purchase #5 $56.95   6.400%   $60.5948   $60.59   $60.60   $60.60  
  Purchase #6 $200.92   11.665%   $224.3573   $224.36   $224.35   $224.40  
  Purchase #7 $196.76   8.312%   $213.1147   $213.11   $213.10   $213.10  
  7 purchase totals = $1,254.79       $1,352.4809   $1,352.48   $1,352.45   $1,352.40