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	$14.60	5.354%	$15.3817	$15.38	$15.40	$15.40
Purchase #2	$13.48	6.355%	$14.3367	$14.34	$14.35	$14.30
Purchase #3	$222.51	11.357%	$247.7805	$247.78	$247.80	$247.80
Purchase #4	$196.33	10.791%	$217.516	$217.52	$217.50	$217.50
Purchase #5	$29.97	7.335%	$32.1683	$32.17	$32.15	$32.20
Purchase #6	$57.27	3.386%	$59.2092	$59.21	$59.20	$59.20
Purchase #7	$240.84	7.323%	$258.4767	$258.48	$258.50	$258.50
7 purchase totals =	$775.00		$844.8691	$844.88	$844.90	$844.90