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	$49.33	8.680%	$53.6118	$53.61	$53.60	$53.60
Purchase #2	$57.77	11.634%	$64.491	$64.49	$64.50	$64.50
Purchase #3	$6.61	8.858%	$7.1955	$7.20	$7.20	$7.20
Purchase #4	$20.84	9.220%	$22.7614	$22.76	$22.75	$22.80
Purchase #5	$48.68	7.458%	$52.3106	$52.31	$52.30	$52.30
Purchase #6	$10.69	7.173%	$11.4568	$11.46	$11.45	$11.50
Purchase #7	$97.92	5.538%	$103.3428	$103.34	$103.35	$103.30
7 purchase totals =	$291.84		$315.1699	$315.17	$315.15	$315.20