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	$190.47	5.243%	$200.4563	$200.46	$200.45	$200.50
Purchase #2	$207.83	8.549%	$225.5974	$225.60	$225.60	$225.60
Purchase #3	$183.71	4.301%	$191.6114	$191.61	$191.60	$191.60
Purchase #4	$79.51	13.535%	$90.2717	$90.27	$90.25	$90.30
Purchase #5	$227.99	13.362%	$258.454	$258.45	$258.45	$258.50
Purchase #6	$29.57	9.267%	$32.3103	$32.31	$32.30	$32.30
Purchase #7	$214.46	3.349%	$221.6423	$221.64	$221.65	$221.60
7 purchase totals =	$1,133.54		$1,220.3434	$1,220.34	$1,220.30	$1,220.40