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 $219.26   11.441%   $244.3455   $244.35   $244.35   $244.30  
  Purchase #2 $183.95   4.593%   $192.3988   $192.40   $192.40   $192.40  
  Purchase #3 $206.44   6.552%   $219.9659   $219.97   $219.95   $220.00  
  Purchase #4 $58.91   11.492%   $65.6799   $65.68   $65.70   $65.70  
  Purchase #5 $138.70   13.779%   $157.8115   $157.81   $157.80   $157.80  
  Purchase #6 $126.37   10.653%   $139.8322   $139.83   $139.85   $139.80  
  Purchase #7 $162.88   13.500%   $184.8688   $184.87   $184.85   $184.90  
  7 purchase totals = $1,096.51       $1,204.9026   $1,204.91   $1,204.90   $1,204.90