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	$168.70	5.667%	$178.2602	$178.26	$178.25	$178.30
Purchase #2	$212.68	4.726%	$222.7313	$222.73	$222.75	$222.70
Purchase #3	$129.64	13.303%	$146.886	$146.89	$146.90	$146.90
Purchase #4	$39.82	13.554%	$45.2172	$45.22	$45.20	$45.20
Purchase #5	$235.90	8.246%	$255.3523	$255.35	$255.35	$255.40
Purchase #6	$195.97	7.733%	$211.1244	$211.12	$211.10	$211.10
Purchase #7	$74.54	8.266%	$80.7015	$80.70	$80.70	$80.70
7 purchase totals =	$1,057.25		$1,140.2729	$1,140.27	$1,140.25	$1,140.30