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	$153.45	5.288%	$161.5644	$161.56	$161.55	$161.60
Purchase #2	$74.99	5.231%	$78.9127	$78.91	$78.90	$78.90
Purchase #3	$208.99	11.706%	$233.4544	$233.45	$233.45	$233.50
Purchase #4	$153.29	8.633%	$166.5235	$166.52	$166.50	$166.50
Purchase #5	$70.76	12.282%	$79.4507	$79.45	$79.45	$79.50
Purchase #6	$25.48	12.300%	$28.614	$28.61	$28.60	$28.60
Purchase #7	$186.35	3.249%	$192.4045	$192.40	$192.40	$192.40
7 purchase totals =	$873.31		$940.9242	$940.90	$940.85	$941.00