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	$52.33	4.779%	$54.8309	$54.83	$54.85	$54.80
Purchase #2	$155.76	8.107%	$168.3875	$168.39	$168.40	$168.40
Purchase #3	$90.28	13.130%	$102.1338	$102.13	$102.15	$102.10
Purchase #4	$208.81	5.584%	$220.47	$220.47	$220.45	$220.50
Purchase #5	$247.99	10.420%	$273.8306	$273.83	$273.85	$273.80
Purchase #6	$214.83	7.117%	$230.1195	$230.12	$230.10	$230.10
Purchase #7	$152.34	13.323%	$172.6363	$172.64	$172.65	$172.60
7 purchase totals =	$1,122.34		$1,222.4086	$1,222.41	$1,222.45	$1,222.30