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	$66.75	6.728%	$71.2409	$71.24	$71.25	$71.20
Purchase #2	$214.90	3.438%	$222.2883	$222.29	$222.30	$222.30
Purchase #3	$96.93	11.454%	$108.0324	$108.03	$108.05	$108.00
Purchase #4	$117.79	8.170%	$127.4134	$127.41	$127.40	$127.40
Purchase #5	$73.39	7.321%	$78.7629	$78.76	$78.75	$78.80
Purchase #6	$11.83	4.732%	$12.3898	$12.39	$12.40	$12.40
Purchase #7	$152.87	6.733%	$163.1627	$163.16	$163.15	$163.20
7 purchase totals =	$734.46		$783.2904	$783.28	$783.30	$783.30