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 $196.46   6.314%   $208.8645   $208.86   $208.85   $208.90  
  Purchase #2 $12.69   5.189%   $13.3485   $13.35   $13.35   $13.30  
  Purchase #3 $206.62   11.178%   $229.716   $229.72   $229.70   $229.70  
  Purchase #4 $53.28   12.357%   $59.8638   $59.86   $59.85   $59.90  
  Purchase #5 $172.97   6.752%   $184.6489   $184.65   $184.65   $184.60  
  Purchase #6 $194.64   5.835%   $205.9972   $206.00   $206.00   $206.00  
  Purchase #7 $200.28   8.620%   $217.5441   $217.54   $217.55   $217.50  
  7 purchase totals = $1,036.94       $1,119.9830   $1,119.98   $1,119.95   $1,119.90