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	$172.40	4.479%	$180.1218	$180.12	$180.10	$180.10
Purchase #2	$9.98	9.760%	$10.954	$10.95	$10.95	$11.00
Purchase #3	$143.59	8.239%	$155.4204	$155.42	$155.40	$155.40
Purchase #4	$65.51	10.661%	$72.494	$72.49	$72.50	$72.50
Purchase #5	$41.88	5.410%	$44.1457	$44.15	$44.15	$44.10
Purchase #6	$33.73	13.433%	$38.261	$38.26	$38.25	$38.30
Purchase #7	$84.56	7.552%	$90.946	$90.95	$90.95	$90.90
7 purchase totals =	$551.65		$592.3429	$592.34	$592.30	$592.30