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	$172.79	13.847%	$196.7162	$196.72	$196.70	$196.70
Purchase #2	$154.65	7.315%	$165.9626	$165.96	$165.95	$166.00
Purchase #3	$209.40	11.429%	$233.3323	$233.33	$233.35	$233.30
Purchase #4	$127.32	8.303%	$137.8914	$137.89	$137.90	$137.90
Purchase #5	$206.45	6.458%	$219.7825	$219.78	$219.80	$219.80
Purchase #6	$199.94	10.571%	$221.0757	$221.08	$221.10	$221.10
Purchase #7	$220.49	6.671%	$235.1989	$235.20	$235.20	$235.20
7 purchase totals =	$1,291.04		$1,409.9596	$1,409.96	$1,410.00	$1,410.00