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	$95.86	4.505%	$100.1785	$100.18	$100.20	$100.20
Purchase #2	$61.25	5.205%	$64.4381	$64.44	$64.45	$64.40
Purchase #3	$37.34	4.328%	$38.9561	$38.96	$38.95	$39.00
Purchase #4	$137.61	11.662%	$153.6581	$153.66	$153.65	$153.70
Purchase #5	$120.77	12.416%	$135.7648	$135.76	$135.75	$135.80
Purchase #6	$111.65	5.277%	$117.5418	$117.54	$117.55	$117.50
Purchase #7	$118.91	7.219%	$127.4941	$127.49	$127.50	$127.50
7 purchase totals =	$683.39		$738.0315	$738.03	$738.05	$738.10