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	$126.52	5.413%	$133.3685	$133.37	$133.35	$133.40
Purchase #2	$116.69	13.852%	$132.8539	$132.85	$132.85	$132.90
Purchase #3	$62.43	8.739%	$67.8858	$67.89	$67.90	$67.90
Purchase #4	$180.26	13.748%	$205.0421	$205.04	$205.05	$205.00
Purchase #5	$149.69	5.817%	$158.3975	$158.40	$158.40	$158.40
Purchase #6	$60.75	13.131%	$68.7271	$68.73	$68.75	$68.70
Purchase #7	$53.49	10.716%	$59.222	$59.22	$59.20	$59.20
7 purchase totals =	$749.83		$825.4969	$825.50	$825.50	$825.50