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	$144.63	10.345%	$159.592	$159.59	$159.60	$159.60
Purchase #2	$42.40	13.252%	$48.0188	$48.02	$48.00	$48.00
Purchase #3	$58.77	10.391%	$64.8768	$64.88	$64.90	$64.90
Purchase #4	$97.94	9.195%	$106.9456	$106.95	$106.95	$106.90
Purchase #5	$114.51	11.286%	$127.4336	$127.43	$127.45	$127.40
Purchase #6	$134.94	10.116%	$148.5905	$148.59	$148.60	$148.60
Purchase #7	$145.72	4.711%	$152.5849	$152.58	$152.60	$152.60
7 purchase totals =	$738.91		$808.0422	$808.04	$808.10	$808.00