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	$37.56	12.405%	$42.2193	$42.22	$42.20	$42.20
Purchase #2	$208.93	6.737%	$223.0056	$223.01	$223.00	$223.00
Purchase #3	$42.51	5.321%	$44.772	$44.77	$44.75	$44.80
Purchase #4	$227.56	6.143%	$241.539	$241.54	$241.55	$241.50
Purchase #5	$227.51	4.475%	$237.6911	$237.69	$237.70	$237.70
Purchase #6	$210.52	12.728%	$237.315	$237.32	$237.30	$237.30
Purchase #7	$43.96	9.839%	$48.2852	$48.29	$48.30	$48.30
7 purchase totals =	$998.55		$1,074.8272	$1,074.84	$1,074.80	$1,074.80