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	$195.67	6.322%	$208.0403	$208.04	$208.05	$208.00
Purchase #2	$33.86	13.485%	$38.426	$38.43	$38.45	$38.40
Purchase #3	$134.77	3.771%	$139.8522	$139.85	$139.85	$139.90
Purchase #4	$157.76	9.223%	$172.3102	$172.31	$172.30	$172.30
Purchase #5	$44.70	11.264%	$49.735	$49.74	$49.75	$49.70
Purchase #6	$43.35	11.379%	$48.2828	$48.28	$48.30	$48.30
Purchase #7	$29.48	10.853%	$32.6795	$32.68	$32.70	$32.70
7 purchase totals =	$639.59		$689.3260	$689.33	$689.40	$689.30