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	$175.34	6.406%	$186.5723	$186.57	$186.55	$186.60
Purchase #2	$184.67	6.523%	$196.716	$196.72	$196.70	$196.70
Purchase #3	$95.92	10.311%	$105.8103	$105.81	$105.80	$105.80
Purchase #4	$122.26	7.514%	$131.4466	$131.45	$131.45	$131.40
Purchase #5	$93.89	10.535%	$103.7813	$103.78	$103.80	$103.80
Purchase #6	$205.46	11.289%	$228.6544	$228.65	$228.65	$228.70
Purchase #7	$222.67	13.443%	$252.6035	$252.60	$252.60	$252.60
7 purchase totals =	$1,100.21		$1,205.5844	$1,205.58	$1,205.55	$1,205.60