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	$46.42	13.314%	$52.6004	$52.60	$52.60	$52.60
Purchase #2	$217.52	11.569%	$242.6849	$242.68	$242.70	$242.70
Purchase #3	$204.59	3.237%	$211.2126	$211.21	$211.20	$211.20
Purchase #4	$210.83	12.204%	$236.5597	$236.56	$236.55	$236.60
Purchase #5	$127.44	3.227%	$131.5525	$131.55	$131.55	$131.60
Purchase #6	$202.25	13.335%	$229.22	$229.22	$229.20	$229.20
Purchase #7	$104.27	7.847%	$112.4521	$112.45	$112.45	$112.50
7 purchase totals =	$1,113.32		$1,216.2822	$1,216.27	$1,216.25	$1,216.40