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	$58.43	12.833%	$65.9283	$65.93	$65.95	$65.90
Purchase #2	$233.95	9.218%	$255.5155	$255.52	$255.50	$255.50
Purchase #3	$229.41	5.308%	$241.5871	$241.59	$241.60	$241.60
Purchase #4	$59.75	13.598%	$67.8748	$67.87	$67.85	$67.90
Purchase #5	$137.82	10.579%	$152.4	$152.40	$152.40	$152.40
Purchase #6	$242.87	4.700%	$254.2849	$254.28	$254.30	$254.30
Purchase #7	$167.83	6.246%	$178.3127	$178.31	$178.30	$178.30
7 purchase totals =	$1,130.06		$1,215.9033	$1,215.90	$1,215.90	$1,215.90