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	$30.29	6.112%	$32.1413	$32.14	$32.15	$32.10
Purchase #2	$63.45	4.505%	$66.3084	$66.31	$66.30	$66.30
Purchase #3	$87.48	10.365%	$96.5473	$96.55	$96.55	$96.50
Purchase #4	$98.42	10.385%	$108.6409	$108.64	$108.65	$108.60
Purchase #5	$164.73	5.181%	$173.2647	$173.26	$173.25	$173.30
Purchase #6	$47.79	12.152%	$53.5974	$53.60	$53.60	$53.60
Purchase #7	$195.45	11.258%	$217.4538	$217.45	$217.45	$217.50
7 purchase totals =	$687.61		$747.9538	$747.95	$747.95	$747.90