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	$166.29	7.761%	$179.1958	$179.20	$179.20	$179.20
Purchase #2	$48.41	9.364%	$52.9431	$52.94	$52.95	$52.90
Purchase #3	$134.50	7.701%	$144.8578	$144.86	$144.85	$144.90
Purchase #4	$128.59	8.433%	$139.434	$139.43	$139.45	$139.40
Purchase #5	$108.55	13.408%	$123.1044	$123.10	$123.10	$123.10
Purchase #6	$113.38	4.191%	$118.1318	$118.13	$118.15	$118.10
Purchase #7	$103.56	8.182%	$112.0333	$112.03	$112.05	$112.00
7 purchase totals =	$803.28		$869.7002	$869.69	$869.75	$869.60