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	$165.45	13.404%	$187.6269	$187.63	$187.65	$187.60
Purchase #2	$210.54	9.589%	$230.7287	$230.73	$230.75	$230.70
Purchase #3	$22.45	7.740%	$24.1876	$24.19	$24.20	$24.20
Purchase #4	$241.79	4.605%	$252.9244	$252.92	$252.90	$252.90
Purchase #5	$100.64	3.230%	$103.8907	$103.89	$103.90	$103.90
Purchase #6	$178.74	5.190%	$188.0166	$188.02	$188.00	$188.00
Purchase #7	$27.86	5.762%	$29.4653	$29.47	$29.45	$29.50
7 purchase totals =	$947.47		$1,016.8402	$1,016.85	$1,016.85	$1,016.80