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	$85.51	12.151%	$95.9003	$95.90	$95.90	$95.90
Purchase #2	$113.64	11.427%	$126.6256	$126.63	$126.65	$126.60
Purchase #3	$150.40	11.130%	$167.1395	$167.14	$167.15	$167.10
Purchase #4	$208.86	11.809%	$233.5243	$233.52	$233.50	$233.50
Purchase #5	$221.64	7.536%	$238.3428	$238.34	$238.35	$238.30
Purchase #6	$152.48	13.644%	$173.2844	$173.28	$173.30	$173.30
Purchase #7	$224.99	13.536%	$255.4446	$255.44	$255.45	$255.40
7 purchase totals =	$1,157.52		$1,290.2615	$1,290.25	$1,290.30	$1,290.10