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	$49.40	13.685%	$56.1604	$56.16	$56.15	$56.20
Purchase #2	$67.54	13.678%	$76.7781	$76.78	$76.80	$76.80
Purchase #3	$73.82	11.222%	$82.1041	$82.10	$82.10	$82.10
Purchase #4	$103.68	10.815%	$114.893	$114.89	$114.90	$114.90
Purchase #5	$236.95	4.388%	$247.3474	$247.35	$247.35	$247.30
Purchase #6	$213.72	6.303%	$227.1908	$227.19	$227.20	$227.20
Purchase #7	$154.39	11.481%	$172.1155	$172.12	$172.10	$172.10
7 purchase totals =	$899.50		$976.5893	$976.59	$976.60	$976.60