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	$96.56	7.285%	$103.5944	$103.59	$103.60	$103.60
Purchase #2	$34.91	9.551%	$38.2443	$38.24	$38.25	$38.20
Purchase #3	$142.28	8.191%	$153.9342	$153.93	$153.95	$153.90
Purchase #4	$100.69	4.416%	$105.1365	$105.14	$105.15	$105.10
Purchase #5	$175.34	13.551%	$199.1003	$199.10	$199.10	$199.10
Purchase #6	$162.65	4.131%	$169.3691	$169.37	$169.35	$169.40
Purchase #7	$112.85	10.649%	$124.8674	$124.87	$124.85	$124.90
7 purchase totals =	$825.28		$894.2462	$894.24	$894.25	$894.20