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	$128.25	13.491%	$145.5522	$145.55	$145.55	$145.60
Purchase #2	$50.94	11.706%	$56.903	$56.90	$56.90	$56.90
Purchase #3	$208.59	7.282%	$223.7795	$223.78	$223.80	$223.80
Purchase #4	$23.29	5.552%	$24.5831	$24.58	$24.60	$24.60
Purchase #5	$105.92	9.214%	$115.6795	$115.68	$115.70	$115.70
Purchase #6	$164.58	8.856%	$179.1552	$179.16	$179.15	$179.20
Purchase #7	$113.59	8.339%	$123.0623	$123.06	$123.05	$123.10
7 purchase totals =	$795.16		$868.7148	$868.71	$868.75	$868.90