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	$152.42	13.412%	$172.8626	$172.86	$172.85	$172.90
Purchase #2	$53.32	11.775%	$59.5984	$59.60	$59.60	$59.60
Purchase #3	$27.55	3.680%	$28.5638	$28.56	$28.55	$28.60
Purchase #4	$132.91	9.362%	$145.353	$145.35	$145.35	$145.40
Purchase #5	$179.68	5.157%	$188.9461	$188.95	$188.95	$188.90
Purchase #6	$146.32	13.371%	$165.8844	$165.88	$165.90	$165.90
Purchase #7	$188.81	8.574%	$204.9986	$205.00	$205.00	$205.00
7 purchase totals =	$881.01		$966.2069	$966.20	$966.20	$966.30