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	$146.81	6.678%	$156.614	$156.61	$156.60	$156.60
Purchase #2	$16.86	5.802%	$17.8382	$17.84	$17.85	$17.80
Purchase #3	$14.49	13.624%	$16.4641	$16.46	$16.45	$16.50
Purchase #4	$11.79	4.292%	$12.296	$12.30	$12.30	$12.30
Purchase #5	$128.98	11.324%	$143.5857	$143.59	$143.60	$143.60
Purchase #6	$146.53	13.126%	$165.7635	$165.76	$165.75	$165.80
Purchase #7	$22.89	13.173%	$25.9053	$25.91	$25.90	$25.90
7 purchase totals =	$488.35		$538.4668	$538.47	$538.45	$538.50