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	$182.79	7.343%	$196.2123	$196.21	$196.20	$196.20
Purchase #2	$228.92	8.242%	$247.7876	$247.79	$247.80	$247.80
Purchase #3	$244.78	12.618%	$275.6663	$275.67	$275.65	$275.70
Purchase #4	$142.26	7.845%	$153.4203	$153.42	$153.40	$153.40
Purchase #5	$77.33	11.870%	$86.5091	$86.51	$86.50	$86.50
Purchase #6	$12.59	5.497%	$13.2821	$13.28	$13.30	$13.30
Purchase #7	$108.39	3.240%	$111.9018	$111.90	$111.90	$111.90
7 purchase totals =	$997.06		$1,084.7795	$1,084.78	$1,084.75	$1,084.80