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	$245.51	7.597%	$264.1614	$264.16	$264.15	$264.20
Purchase #2	$100.41	11.399%	$111.8557	$111.86	$111.85	$111.90
Purchase #3	$60.27	4.131%	$62.7598	$62.76	$62.75	$62.80
Purchase #4	$204.70	7.401%	$219.8498	$219.85	$219.85	$219.80
Purchase #5	$30.72	13.118%	$34.7498	$34.75	$34.75	$34.70
Purchase #6	$169.88	9.780%	$186.4943	$186.49	$186.50	$186.50
Purchase #7	$207.88	12.204%	$233.2497	$233.25	$233.25	$233.20
7 purchase totals =	$1,019.37		$1,113.1205	$1,113.12	$1,113.10	$1,113.10