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	$11.28	5.423%	$11.8917	$11.89	$11.90	$11.90
Purchase #2	$53.68	10.185%	$59.1473	$59.15	$59.15	$59.10
Purchase #3	$207.31	5.324%	$218.3472	$218.35	$218.35	$218.30
Purchase #4	$66.68	5.161%	$70.1214	$70.12	$70.10	$70.10
Purchase #5	$197.74	5.476%	$208.5682	$208.57	$208.55	$208.60
Purchase #6	$145.44	5.298%	$153.1454	$153.15	$153.15	$153.10
Purchase #7	$143.32	5.652%	$151.4204	$151.42	$151.40	$151.40
7 purchase totals =	$825.45		$872.6416	$872.65	$872.60	$872.50