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	$78.47	4.580%	$82.0639	$82.06	$82.05	$82.10
Purchase #2	$223.38	8.161%	$241.61	$241.61	$241.60	$241.60
Purchase #3	$234.26	8.351%	$253.8231	$253.82	$253.80	$253.80
Purchase #4	$80.70	8.622%	$87.658	$87.66	$87.65	$87.70
Purchase #5	$219.85	4.303%	$229.3101	$229.31	$229.30	$229.30
Purchase #6	$197.43	10.873%	$218.8966	$218.90	$218.90	$218.90
Purchase #7	$211.38	9.689%	$231.8606	$231.86	$231.85	$231.90
7 purchase totals =	$1,245.47		$1,345.2223	$1,345.22	$1,345.15	$1,345.30