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	$217.80	12.143%	$244.2475	$244.25	$244.25	$244.20
Purchase #2	$11.83	4.170%	$12.3233	$12.32	$12.30	$12.30
Purchase #3	$232.63	10.142%	$256.2233	$256.22	$256.20	$256.20
Purchase #4	$243.27	10.779%	$269.4921	$269.49	$269.50	$269.50
Purchase #5	$207.73	11.118%	$230.8254	$230.83	$230.85	$230.80
Purchase #6	$131.97	9.253%	$144.1812	$144.18	$144.20	$144.20
Purchase #7	$85.95	5.434%	$90.6205	$90.62	$90.60	$90.60
7 purchase totals =	$1,131.18		$1,247.9133	$1,247.91	$1,247.90	$1,247.80