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	$27.41	5.256%	$28.8507	$28.85	$28.85	$28.90
Purchase #2	$141.56	7.408%	$152.0468	$152.05	$152.05	$152.00
Purchase #3	$205.69	8.455%	$223.0811	$223.08	$223.10	$223.10
Purchase #4	$146.82	13.175%	$166.1635	$166.16	$166.15	$166.20
Purchase #5	$46.25	11.399%	$51.522	$51.52	$51.50	$51.50
Purchase #6	$107.87	8.382%	$116.9117	$116.91	$116.90	$116.90
Purchase #7	$231.67	10.385%	$255.7289	$255.73	$255.75	$255.70
7 purchase totals =	$907.27		$994.3047	$994.30	$994.30	$994.30