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	$240.43	7.863%	$259.335	$259.34	$259.35	$259.30
Purchase #2	$158.73	4.403%	$165.7189	$165.72	$165.70	$165.70
Purchase #3	$90.71	8.622%	$98.531	$98.53	$98.55	$98.50
Purchase #4	$16.93	10.411%	$18.6926	$18.69	$18.70	$18.70
Purchase #5	$248.42	9.208%	$271.2945	$271.29	$271.30	$271.30
Purchase #6	$146.46	5.445%	$154.4347	$154.43	$154.45	$154.40
Purchase #7	$179.35	11.436%	$199.8605	$199.86	$199.85	$199.90
7 purchase totals =	$1,081.03		$1,167.8672	$1,167.86	$1,167.90	$1,167.80