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	$137.84	11.414%	$153.5731	$153.57	$153.55	$153.60
Purchase #2	$81.68	7.157%	$87.5258	$87.53	$87.55	$87.50
Purchase #3	$74.49	10.134%	$82.0388	$82.04	$82.05	$82.00
Purchase #4	$56.42	5.561%	$59.5575	$59.56	$59.55	$59.60
Purchase #5	$72.56	3.104%	$74.8123	$74.81	$74.80	$74.80
Purchase #6	$219.38	3.593%	$227.2623	$227.26	$227.25	$227.30
Purchase #7	$33.51	12.259%	$37.618	$37.62	$37.60	$37.60
7 purchase totals =	$675.88		$722.3878	$722.39	$722.35	$722.40