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	$219.65	10.221%	$242.1004	$242.10	$242.10	$242.10
Purchase #2	$100.74	8.701%	$109.5054	$109.51	$109.50	$109.50
Purchase #3	$14.85	3.604%	$15.3852	$15.39	$15.40	$15.40
Purchase #4	$197.60	8.588%	$214.5699	$214.57	$214.55	$214.60
Purchase #5	$92.68	13.794%	$105.4643	$105.46	$105.45	$105.50
Purchase #6	$166.86	7.806%	$179.8851	$179.89	$179.90	$179.90
Purchase #7	$45.55	6.367%	$48.4502	$48.45	$48.45	$48.50
7 purchase totals =	$837.93		$915.3605	$915.37	$915.35	$915.50