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 $56.35   8.213%   $60.978   $60.98   $61.00   $61.00  
  Purchase #2 $215.56   8.383%   $233.6304   $233.63   $233.65   $233.60  
  Purchase #3 $214.57   10.854%   $237.8594   $237.86   $237.85   $237.90  
  Purchase #4 $111.92   10.686%   $123.8798   $123.88   $123.90   $123.90  
  Purchase #5 $176.31   12.409%   $198.1883   $198.19   $198.20   $198.20  
  Purchase #6 $250.77   9.233%   $273.9236   $273.92   $273.90   $273.90  
  Purchase #7 $44.75   11.441%   $49.8698   $49.87   $49.85   $49.90  
  7 purchase totals = $1,070.23       $1,178.3293   $1,178.33   $1,178.35   $1,178.40