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	$98.48	13.557%	$111.8309	$111.83	$111.85	$111.80
Purchase #2	$138.60	10.187%	$152.7192	$152.72	$152.70	$152.70
Purchase #3	$143.78	10.377%	$158.7001	$158.70	$158.70	$158.70
Purchase #4	$197.84	10.497%	$218.6073	$218.61	$218.60	$218.60
Purchase #5	$210.34	7.493%	$226.1008	$226.10	$226.10	$226.10
Purchase #6	$53.43	6.510%	$56.9083	$56.91	$56.90	$56.90
Purchase #7	$77.25	13.666%	$87.807	$87.81	$87.80	$87.80
7 purchase totals =	$919.72		$1,012.6736	$1,012.68	$1,012.65	$1,012.60