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	$66.64	13.205%	$75.4398	$75.44	$75.45	$75.40
Purchase #2	$46.64	11.830%	$52.1575	$52.16	$52.15	$52.20
Purchase #3	$78.96	3.104%	$81.4109	$81.41	$81.40	$81.40
Purchase #4	$28.58	8.824%	$31.1019	$31.10	$31.10	$31.10
Purchase #5	$19.72	12.333%	$22.1521	$22.15	$22.15	$22.20
Purchase #6	$144.80	4.501%	$151.3174	$151.32	$151.30	$151.30
Purchase #7	$105.82	5.357%	$111.4888	$111.49	$111.50	$111.50
7 purchase totals =	$491.16		$525.0684	$525.07	$525.05	$525.10