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	$237.33	7.639%	$255.4596	$255.46	$255.45	$255.50
Purchase #2	$62.61	13.169%	$70.8551	$70.86	$70.85	$70.90
Purchase #3	$59.40	5.410%	$62.6135	$62.61	$62.60	$62.60
Purchase #4	$70.61	12.709%	$79.5838	$79.58	$79.60	$79.60
Purchase #5	$67.74	9.222%	$73.987	$73.99	$74.00	$74.00
Purchase #6	$55.89	6.626%	$59.5933	$59.59	$59.60	$59.60
Purchase #7	$220.65	12.212%	$247.5958	$247.60	$247.60	$247.60
7 purchase totals =	$774.23		$849.6881	$849.69	$849.70	$849.80