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	$151.70	13.597%	$172.3266	$172.33	$172.35	$172.30
Purchase #2	$165.92	13.678%	$188.6145	$188.61	$188.60	$188.60
Purchase #3	$161.25	11.472%	$179.7486	$179.75	$179.75	$179.70
Purchase #4	$203.32	6.462%	$216.4585	$216.46	$216.45	$216.50
Purchase #5	$78.48	8.718%	$85.3219	$85.32	$85.30	$85.30
Purchase #6	$238.37	3.796%	$247.4185	$247.42	$247.40	$247.40
Purchase #7	$204.42	10.378%	$225.6347	$225.63	$225.65	$225.60
7 purchase totals =	$1,203.46		$1,315.5233	$1,315.52	$1,315.50	$1,315.40