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	$250.93	12.635%	$282.635	$282.64	$282.65	$282.60
Purchase #2	$92.60	13.556%	$105.1529	$105.15	$105.15	$105.20
Purchase #3	$127.29	3.552%	$131.8113	$131.81	$131.80	$131.80
Purchase #4	$124.71	6.467%	$132.775	$132.78	$132.80	$132.80
Purchase #5	$41.62	5.586%	$43.9449	$43.94	$43.95	$43.90
Purchase #6	$54.70	10.359%	$60.3664	$60.37	$60.35	$60.40
Purchase #7	$59.62	12.796%	$67.249	$67.25	$67.25	$67.20
7 purchase totals =	$751.47		$823.9345	$823.94	$823.95	$823.90