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	$133.67	13.460%	$151.662	$151.66	$151.65	$151.70
Purchase #2	$50.33	10.823%	$55.7772	$55.78	$55.80	$55.80
Purchase #3	$82.77	12.718%	$93.2967	$93.30	$93.30	$93.30
Purchase #4	$173.72	8.665%	$188.7728	$188.77	$188.75	$188.80
Purchase #5	$200.71	9.130%	$219.0348	$219.03	$219.05	$219.00
Purchase #6	$69.35	12.803%	$78.2289	$78.23	$78.25	$78.20
Purchase #7	$121.71	4.724%	$127.4596	$127.46	$127.45	$127.50
7 purchase totals =	$832.26		$914.2320	$914.23	$914.25	$914.30