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	$44.72	10.868%	$49.5802	$49.58	$49.60	$49.60
Purchase #2	$66.31	7.838%	$71.5074	$71.51	$71.50	$71.50
Purchase #3	$9.61	6.785%	$10.262	$10.26	$10.25	$10.30
Purchase #4	$237.31	12.335%	$266.5822	$266.58	$266.60	$266.60
Purchase #5	$182.83	6.385%	$194.5037	$194.50	$194.50	$194.50
Purchase #6	$153.25	13.481%	$173.9096	$173.91	$173.90	$173.90
Purchase #7	$83.38	10.240%	$91.9181	$91.92	$91.90	$91.90
7 purchase totals =	$777.41		$858.2632	$858.26	$858.25	$858.30