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	$226.60	3.224%	$233.9056	$233.91	$233.90	$233.90
Purchase #2	$209.76	3.581%	$217.2715	$217.27	$217.25	$217.30
Purchase #3	$146.87	3.380%	$151.8342	$151.83	$151.85	$151.80
Purchase #4	$89.62	13.191%	$101.4418	$101.44	$101.45	$101.40
Purchase #5	$233.63	11.816%	$261.2357	$261.24	$261.25	$261.20
Purchase #6	$107.40	3.750%	$111.4275	$111.43	$111.45	$111.40
Purchase #7	$71.68	5.704%	$75.7686	$75.77	$75.75	$75.80
7 purchase totals =	$1,085.56		$1,152.8849	$1,152.89	$1,152.90	$1,152.80