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	$126.78	5.145%	$133.3028	$133.30	$133.30	$133.30
Purchase #2	$100.61	6.634%	$107.2845	$107.28	$107.30	$107.30
Purchase #3	$194.27	7.267%	$208.3876	$208.39	$208.40	$208.40
Purchase #4	$82.50	11.171%	$91.7161	$91.72	$91.70	$91.70
Purchase #5	$155.83	11.177%	$173.2471	$173.25	$173.25	$173.20
Purchase #6	$222.54	7.344%	$238.8833	$238.88	$238.90	$238.90
Purchase #7	$25.90	11.603%	$28.9052	$28.91	$28.90	$28.90
7 purchase totals =	$908.43		$981.7266	$981.73	$981.75	$981.70