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	$135.29	13.433%	$153.4635	$153.46	$153.45	$153.50
Purchase #2	$142.31	11.595%	$158.8108	$158.81	$158.80	$158.80
Purchase #3	$54.47	5.747%	$57.6004	$57.60	$57.60	$57.60
Purchase #4	$13.92	4.123%	$14.4939	$14.49	$14.50	$14.50
Purchase #5	$94.48	10.449%	$104.3522	$104.35	$104.35	$104.40
Purchase #6	$160.44	3.132%	$165.465	$165.47	$165.45	$165.50
Purchase #7	$132.98	11.256%	$147.9482	$147.95	$147.95	$147.90
7 purchase totals =	$733.89		$802.1340	$802.13	$802.10	$802.20