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	$118.74	4.775%	$124.4098	$124.41	$124.40	$124.40
Purchase #2	$222.26	3.107%	$229.1656	$229.17	$229.15	$229.20
Purchase #3	$127.25	10.743%	$140.9205	$140.92	$140.90	$140.90
Purchase #4	$244.46	4.258%	$254.8691	$254.87	$254.85	$254.90
Purchase #5	$32.95	4.125%	$34.3092	$34.31	$34.30	$34.30
Purchase #6	$92.98	13.672%	$105.6922	$105.69	$105.70	$105.70
Purchase #7	$238.54	10.199%	$262.8687	$262.87	$262.85	$262.90
7 purchase totals =	$1,077.18		$1,152.2351	$1,152.24	$1,152.15	$1,152.30