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	$115.53	10.698%	$127.8894	$127.89	$127.90	$127.90
Purchase #2	$180.26	4.739%	$188.8025	$188.80	$188.80	$188.80
Purchase #3	$239.31	5.415%	$252.2686	$252.27	$252.25	$252.30
Purchase #4	$217.56	5.204%	$228.8818	$228.88	$228.90	$228.90
Purchase #5	$145.71	3.152%	$150.3028	$150.30	$150.30	$150.30
Purchase #6	$185.88	5.508%	$196.1183	$196.12	$196.10	$196.10
Purchase #7	$157.38	3.416%	$162.7561	$162.76	$162.75	$162.80
7 purchase totals =	$1,241.63		$1,307.0195	$1,307.02	$1,307.00	$1,307.10