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	$191.35	13.592%	$217.3583	$217.36	$217.35	$217.40
Purchase #2	$72.85	5.126%	$76.5843	$76.58	$76.60	$76.60
Purchase #3	$166.82	3.798%	$173.1558	$173.16	$173.15	$173.20
Purchase #4	$89.88	10.634%	$99.4378	$99.44	$99.45	$99.40
Purchase #5	$211.31	10.226%	$232.9186	$232.92	$232.90	$232.90
Purchase #6	$40.38	12.801%	$45.549	$45.55	$45.55	$45.50
Purchase #7	$233.91	9.215%	$255.4648	$255.46	$255.45	$255.50
7 purchase totals =	$1,006.50		$1,100.4686	$1,100.47	$1,100.45	$1,100.50