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	$98.61	4.823%	$103.366	$103.37	$103.35	$103.40
Purchase #2	$126.26	11.362%	$140.6057	$140.61	$140.60	$140.60
Purchase #3	$94.25	13.400%	$106.8795	$106.88	$106.90	$106.90
Purchase #4	$19.58	9.621%	$21.4638	$21.46	$21.45	$21.50
Purchase #5	$111.92	10.313%	$123.4623	$123.46	$123.45	$123.50
Purchase #6	$121.53	9.375%	$132.9234	$132.92	$132.90	$132.90
Purchase #7	$230.37	6.449%	$245.2266	$245.23	$245.25	$245.20
7 purchase totals =	$802.52		$873.9273	$873.93	$873.90	$874.00