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	$160.55	7.545%	$172.6635	$172.66	$172.65	$172.70
Purchase #2	$168.92	5.463%	$178.1481	$178.15	$178.15	$178.10
Purchase #3	$98.43	8.761%	$107.0535	$107.05	$107.05	$107.10
Purchase #4	$63.83	5.776%	$67.5168	$67.52	$67.50	$67.50
Purchase #5	$47.47	6.175%	$50.4013	$50.40	$50.40	$50.40
Purchase #6	$153.58	4.113%	$159.8967	$159.90	$159.90	$159.90
Purchase #7	$48.92	3.134%	$50.4532	$50.45	$50.45	$50.50
7 purchase totals =	$741.70		$786.1331	$786.13	$786.10	$786.20