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	$56.78	4.376%	$59.2647	$59.26	$59.25	$59.30
Purchase #2	$186.51	11.475%	$207.912	$207.91	$207.90	$207.90
Purchase #3	$158.86	5.555%	$167.6847	$167.68	$167.70	$167.70
Purchase #4	$20.55	13.114%	$23.2449	$23.24	$23.25	$23.20
Purchase #5	$37.93	13.113%	$42.9038	$42.90	$42.90	$42.90
Purchase #6	$176.97	10.820%	$196.1182	$196.12	$196.10	$196.10
Purchase #7	$92.63	10.726%	$102.5655	$102.57	$102.55	$102.60
7 purchase totals =	$730.23		$799.6938	$799.68	$799.65	$799.70