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	$154.42	12.581%	$173.8476	$173.85	$173.85	$173.80
Purchase #2	$167.41	4.828%	$175.4926	$175.49	$175.50	$175.50
Purchase #3	$122.62	11.788%	$137.0744	$137.07	$137.05	$137.10
Purchase #4	$78.93	12.619%	$88.8902	$88.89	$88.90	$88.90
Purchase #5	$41.60	4.664%	$43.5402	$43.54	$43.55	$43.50
Purchase #6	$61.78	8.586%	$67.0844	$67.08	$67.10	$67.10
Purchase #7	$237.42	12.244%	$266.4897	$266.49	$266.50	$266.50
7 purchase totals =	$864.18		$952.4191	$952.41	$952.45	$952.40