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	$165.95	4.421%	$173.2866	$173.29	$173.30	$173.30
Purchase #2	$53.86	11.387%	$59.993	$59.99	$60.00	$60.00
Purchase #3	$78.41	6.865%	$83.7928	$83.79	$83.80	$83.80
Purchase #4	$101.89	6.479%	$108.4915	$108.49	$108.50	$108.50
Purchase #5	$99.37	7.262%	$106.5862	$106.59	$106.60	$106.60
Purchase #6	$20.35	6.351%	$21.6424	$21.64	$21.65	$21.60
Purchase #7	$149.39	6.534%	$159.1511	$159.15	$159.15	$159.20
7 purchase totals =	$669.22		$712.9436	$712.94	$713.00	$713.00