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	$71.71	4.343%	$74.8244	$74.82	$74.80	$74.80
Purchase #2	$221.76	4.728%	$232.2448	$232.24	$232.25	$232.20
Purchase #3	$99.96	5.385%	$105.3428	$105.34	$105.35	$105.30
Purchase #4	$42.39	7.145%	$45.4188	$45.42	$45.40	$45.40
Purchase #5	$233.81	7.147%	$250.5204	$250.52	$250.50	$250.50
Purchase #6	$138.96	5.139%	$146.1012	$146.10	$146.10	$146.10
Purchase #7	$237.47	3.133%	$244.9099	$244.91	$244.90	$244.90
7 purchase totals =	$1,046.06		$1,099.3623	$1,099.35	$1,099.30	$1,099.20