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	$62.34	4.521%	$65.1584	$65.16	$65.15	$65.20
Purchase #2	$201.40	7.286%	$216.074	$216.07	$216.05	$216.10
Purchase #3	$68.41	13.687%	$77.7733	$77.77	$77.75	$77.80
Purchase #4	$235.89	13.707%	$268.2234	$268.22	$268.20	$268.20
Purchase #5	$231.69	7.518%	$249.1085	$249.11	$249.10	$249.10
Purchase #6	$150.53	9.399%	$164.6783	$164.68	$164.70	$164.70
Purchase #7	$101.88	9.361%	$111.417	$111.42	$111.40	$111.40
7 purchase totals =	$1,052.14		$1,152.4329	$1,152.43	$1,152.35	$1,152.50