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	$222.81	7.116%	$238.6652	$238.67	$238.65	$238.70
Purchase #2	$48.77	9.534%	$53.4197	$53.42	$53.40	$53.40
Purchase #3	$233.65	5.832%	$247.2765	$247.28	$247.30	$247.30
Purchase #4	$132.75	4.571%	$138.818	$138.82	$138.80	$138.80
Purchase #5	$209.91	4.540%	$219.4399	$219.44	$219.45	$219.40
Purchase #6	$71.48	10.267%	$78.8189	$78.82	$78.80	$78.80
Purchase #7	$239.57	4.609%	$250.6118	$250.61	$250.60	$250.60
7 purchase totals =	$1,158.94		$1,227.0500	$1,227.06	$1,227.00	$1,227.00