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	$58.62	13.690%	$66.6451	$66.65	$66.65	$66.60
Purchase #2	$181.45	8.607%	$197.0674	$197.07	$197.05	$197.10
Purchase #3	$82.39	9.405%	$90.1388	$90.14	$90.15	$90.10
Purchase #4	$211.99	10.146%	$233.4985	$233.50	$233.50	$233.50
Purchase #5	$144.31	13.749%	$164.1512	$164.15	$164.15	$164.20
Purchase #6	$241.48	5.706%	$255.2588	$255.26	$255.25	$255.30
Purchase #7	$68.90	3.162%	$71.0786	$71.08	$71.10	$71.10
7 purchase totals =	$989.14		$1,077.8384	$1,077.85	$1,077.85	$1,077.90