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	$212.60	4.793%	$222.7899	$222.79	$222.80	$222.80
Purchase #2	$99.91	12.388%	$112.2869	$112.29	$112.30	$112.30
Purchase #3	$119.81	6.604%	$127.7223	$127.72	$127.70	$127.70
Purchase #4	$93.58	10.186%	$103.1121	$103.11	$103.10	$103.10
Purchase #5	$92.82	8.688%	$100.8842	$100.88	$100.90	$100.90
Purchase #6	$157.34	12.489%	$176.9902	$176.99	$177.00	$177.00
Purchase #7	$105.65	3.151%	$108.979	$108.98	$109.00	$109.00
7 purchase totals =	$881.71		$952.7646	$952.76	$952.80	$952.80