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	$80.82	5.389%	$85.1754	$85.18	$85.20	$85.20
Purchase #2	$77.43	6.194%	$82.226	$82.23	$82.25	$82.20
Purchase #3	$40.39	10.383%	$44.5837	$44.58	$44.60	$44.60
Purchase #4	$167.82	5.241%	$176.6154	$176.62	$176.60	$176.60
Purchase #5	$207.41	3.556%	$214.7855	$214.79	$214.80	$214.80
Purchase #6	$197.58	6.431%	$210.2864	$210.29	$210.30	$210.30
Purchase #7	$241.84	12.404%	$271.8378	$271.84	$271.85	$271.80
7 purchase totals =	$1,013.29		$1,085.5102	$1,085.53	$1,085.60	$1,085.50