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	$238.37	9.422%	$260.8292	$260.83	$260.85	$260.80
Purchase #2	$37.45	10.427%	$41.3549	$41.35	$41.35	$41.40
Purchase #3	$156.57	10.178%	$172.5057	$172.51	$172.50	$172.50
Purchase #4	$186.41	7.340%	$200.0925	$200.09	$200.10	$200.10
Purchase #5	$128.95	3.789%	$133.8359	$133.84	$133.85	$133.80
Purchase #6	$58.33	6.345%	$62.031	$62.03	$62.05	$62.00
Purchase #7	$145.93	9.213%	$159.3745	$159.37	$159.35	$159.40
7 purchase totals =	$952.01		$1,030.0237	$1,030.02	$1,030.05	$1,030.00