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	$159.31	10.216%	$175.5851	$175.59	$175.60	$175.60
Purchase #2	$158.82	6.654%	$169.3879	$169.39	$169.40	$169.40
Purchase #3	$224.72	13.321%	$254.655	$254.66	$254.65	$254.70
Purchase #4	$99.75	11.404%	$111.1255	$111.13	$111.15	$111.10
Purchase #5	$53.26	12.162%	$59.7375	$59.74	$59.75	$59.70
Purchase #6	$13.27	6.153%	$14.0865	$14.09	$14.10	$14.10
Purchase #7	$211.78	5.421%	$223.2606	$223.26	$223.25	$223.30
7 purchase totals =	$920.91		$1,007.8381	$1,007.86	$1,007.90	$1,007.90