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	$153.76	11.158%	$170.9165	$170.92	$170.90	$170.90
Purchase #2	$18.59	12.670%	$20.9454	$20.95	$20.95	$20.90
Purchase #3	$178.35	9.658%	$195.575	$195.58	$195.60	$195.60
Purchase #4	$117.94	4.308%	$123.0209	$123.02	$123.00	$123.00
Purchase #5	$247.87	12.784%	$279.5577	$279.56	$279.55	$279.60
Purchase #6	$148.41	3.469%	$153.5583	$153.56	$153.55	$153.60
Purchase #7	$65.42	7.816%	$70.5332	$70.53	$70.55	$70.50
7 purchase totals =	$930.34		$1,014.1070	$1,014.12	$1,014.10	$1,014.10