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	$212.31	6.324%	$225.7365	$225.74	$225.75	$225.70
Purchase #2	$219.66	6.162%	$233.1954	$233.20	$233.20	$233.20
Purchase #3	$172.41	11.110%	$191.5648	$191.56	$191.55	$191.60
Purchase #4	$111.69	10.489%	$123.4052	$123.41	$123.40	$123.40
Purchase #5	$136.27	6.386%	$144.9722	$144.97	$144.95	$145.00
Purchase #6	$127.74	13.187%	$144.5851	$144.59	$144.60	$144.60
Purchase #7	$53.93	11.725%	$60.2533	$60.25	$60.25	$60.30
7 purchase totals =	$1,034.01		$1,123.7125	$1,123.72	$1,123.70	$1,123.80