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	$156.58	5.347%	$164.9523	$164.95	$164.95	$165.00
Purchase #2	$136.85	3.319%	$141.3921	$141.39	$141.40	$141.40
Purchase #3	$158.60	13.456%	$179.9412	$179.94	$179.95	$179.90
Purchase #4	$49.58	13.491%	$56.2688	$56.27	$56.25	$56.30
Purchase #5	$100.76	13.202%	$114.0623	$114.06	$114.05	$114.10
Purchase #6	$192.66	13.302%	$218.2876	$218.29	$218.30	$218.30
Purchase #7	$234.59	7.672%	$252.5877	$252.59	$252.60	$252.60
7 purchase totals =	$1,029.62		$1,127.4920	$1,127.49	$1,127.50	$1,127.60