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	$118.68	10.609%	$131.2708	$131.27	$131.25	$131.30
Purchase #2	$105.98	9.634%	$116.1901	$116.19	$116.20	$116.20
Purchase #3	$205.45	13.852%	$233.9089	$233.91	$233.90	$233.90
Purchase #4	$167.40	3.696%	$173.5871	$173.59	$173.60	$173.60
Purchase #5	$152.69	4.461%	$159.5015	$159.50	$159.50	$159.50
Purchase #6	$158.31	4.728%	$165.7949	$165.79	$165.80	$165.80
Purchase #7	$48.81	4.500%	$51.0065	$51.01	$51.00	$51.00
7 purchase totals =	$957.32		$1,031.2598	$1,031.26	$1,031.25	$1,031.30