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	$235.96	13.114%	$266.9038	$266.90	$266.90	$266.90
Purchase #2	$188.45	11.145%	$209.4528	$209.45	$209.45	$209.50
Purchase #3	$107.87	9.635%	$118.2633	$118.26	$118.25	$118.30
Purchase #4	$72.64	8.609%	$78.8936	$78.89	$78.90	$78.90
Purchase #5	$105.92	4.477%	$110.662	$110.66	$110.65	$110.70
Purchase #6	$141.97	3.632%	$147.1264	$147.13	$147.15	$147.10
Purchase #7	$220.51	4.729%	$230.9379	$230.94	$230.95	$230.90
7 purchase totals =	$1,073.32		$1,162.2398	$1,162.23	$1,162.25	$1,162.30