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	$233.79	7.803%	$252.0326	$252.03	$252.05	$252.00
Purchase #2	$43.40	12.649%	$48.8897	$48.89	$48.90	$48.90
Purchase #3	$80.32	12.812%	$90.6106	$90.61	$90.60	$90.60
Purchase #4	$196.60	6.437%	$209.2551	$209.26	$209.25	$209.30
Purchase #5	$234.39	3.193%	$241.8741	$241.87	$241.85	$241.90
Purchase #6	$192.28	11.626%	$214.6345	$214.63	$214.65	$214.60
Purchase #7	$75.75	8.418%	$82.1266	$82.13	$82.15	$82.10
7 purchase totals =	$1,056.53		$1,139.4232	$1,139.42	$1,139.45	$1,139.40