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	$117.64	8.513%	$127.6547	$127.65	$127.65	$127.70
Purchase #2	$235.87	8.191%	$255.1901	$255.19	$255.20	$255.20
Purchase #3	$81.25	5.356%	$85.6018	$85.60	$85.60	$85.60
Purchase #4	$99.78	13.103%	$112.8542	$112.85	$112.85	$112.90
Purchase #5	$230.30	10.447%	$254.3594	$254.36	$254.35	$254.40
Purchase #6	$194.50	7.574%	$209.2314	$209.23	$209.25	$209.20
Purchase #7	$26.82	9.415%	$29.3451	$29.35	$29.35	$29.30
7 purchase totals =	$986.16		$1,074.2367	$1,074.23	$1,074.25	$1,074.30