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	$139.58	13.575%	$158.528	$158.53	$158.55	$158.50
Purchase #2	$139.56	6.131%	$148.1164	$148.12	$148.10	$148.10
Purchase #3	$51.93	6.671%	$55.3943	$55.39	$55.40	$55.40
Purchase #4	$180.77	3.496%	$187.0897	$187.09	$187.10	$187.10
Purchase #5	$80.71	11.662%	$90.1224	$90.12	$90.10	$90.10
Purchase #6	$21.38	6.782%	$22.83	$22.83	$22.85	$22.80
Purchase #7	$118.67	6.824%	$126.768	$126.77	$126.75	$126.80
7 purchase totals =	$732.60		$788.8488	$788.85	$788.85	$788.80