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	$204.97	5.470%	$216.1819	$216.18	$216.20	$216.20
Purchase #2	$57.37	9.379%	$62.7507	$62.75	$62.75	$62.80
Purchase #3	$36.54	5.456%	$38.5336	$38.53	$38.55	$38.50
Purchase #4	$173.38	7.627%	$186.6037	$186.60	$186.60	$186.60
Purchase #5	$92.50	3.258%	$95.5137	$95.51	$95.50	$95.50
Purchase #6	$9.50	11.275%	$10.5711	$10.57	$10.55	$10.60
Purchase #7	$146.30	12.293%	$164.2847	$164.28	$164.30	$164.30
7 purchase totals =	$720.56		$774.4394	$774.42	$774.45	$774.50