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	$172.80	13.682%	$196.4425	$196.44	$196.45	$196.40
Purchase #2	$230.41	11.152%	$256.1053	$256.11	$256.10	$256.10
Purchase #3	$153.86	11.561%	$171.6478	$171.65	$171.65	$171.60
Purchase #4	$107.68	5.699%	$113.8167	$113.82	$113.80	$113.80
Purchase #5	$11.82	7.679%	$12.7277	$12.73	$12.75	$12.70
Purchase #6	$46.42	12.314%	$52.1362	$52.14	$52.15	$52.10
Purchase #7	$99.92	3.752%	$103.669	$103.67	$103.65	$103.70
7 purchase totals =	$822.91		$906.5452	$906.56	$906.55	$906.40