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	$62.51	8.647%	$67.9152	$67.92	$67.90	$67.90
Purchase #2	$149.68	10.296%	$165.0911	$165.09	$165.10	$165.10
Purchase #3	$223.56	6.513%	$238.1205	$238.12	$238.10	$238.10
Purchase #4	$234.45	7.562%	$252.1791	$252.18	$252.20	$252.20
Purchase #5	$121.39	4.594%	$126.9667	$126.97	$126.95	$127.00
Purchase #6	$100.33	10.873%	$111.2389	$111.24	$111.25	$111.20
Purchase #7	$89.83	8.857%	$97.7862	$97.79	$97.80	$97.80
7 purchase totals =	$981.75		$1,059.2977	$1,059.31	$1,059.30	$1,059.30