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	$211.29	12.824%	$238.3858	$238.39	$238.40	$238.40
Purchase #2	$49.94	11.127%	$55.4968	$55.50	$55.50	$55.50
Purchase #3	$114.32	3.301%	$118.0937	$118.09	$118.10	$118.10
Purchase #4	$249.93	10.147%	$275.2904	$275.29	$275.30	$275.30
Purchase #5	$102.77	8.433%	$111.4366	$111.44	$111.45	$111.40
Purchase #6	$21.91	5.362%	$23.0848	$23.08	$23.10	$23.10
Purchase #7	$165.93	11.726%	$185.387	$185.39	$185.40	$185.40
7 purchase totals =	$916.09		$1,007.1751	$1,007.18	$1,007.25	$1,007.20