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	$241.42	9.616%	$264.6349	$264.63	$264.65	$264.60
Purchase #2	$110.91	7.667%	$119.4135	$119.41	$119.40	$119.40
Purchase #3	$176.89	5.286%	$186.2404	$186.24	$186.25	$186.20
Purchase #4	$77.84	6.494%	$82.8949	$82.89	$82.90	$82.90
Purchase #5	$33.37	3.217%	$34.4435	$34.44	$34.45	$34.40
Purchase #6	$146.39	8.172%	$158.353	$158.35	$158.35	$158.40
Purchase #7	$14.77	3.665%	$15.3113	$15.31	$15.30	$15.30
7 purchase totals =	$801.59		$861.2915	$861.27	$861.30	$861.20