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	$131.25	13.215%	$148.5947	$148.59	$148.60	$148.60
Purchase #2	$21.99	6.812%	$23.488	$23.49	$23.50	$23.50
Purchase #3	$238.37	11.840%	$266.593	$266.59	$266.60	$266.60
Purchase #4	$173.42	3.378%	$179.2781	$179.28	$179.30	$179.30
Purchase #5	$81.66	10.350%	$90.1118	$90.11	$90.10	$90.10
Purchase #6	$151.98	5.278%	$160.0015	$160.00	$160.00	$160.00
Purchase #7	$11.87	4.391%	$12.3912	$12.39	$12.40	$12.40
7 purchase totals =	$810.54		$880.4583	$880.45	$880.50	$880.50