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	$228.89	5.815%	$242.2	$242.20	$242.20	$242.20
Purchase #2	$223.41	8.556%	$242.525	$242.53	$242.55	$242.50
Purchase #3	$72.66	13.680%	$82.5999	$82.60	$82.60	$82.60
Purchase #4	$247.61	8.178%	$267.8595	$267.86	$267.85	$267.90
Purchase #5	$122.99	13.388%	$139.4559	$139.46	$139.45	$139.50
Purchase #6	$169.30	12.730%	$190.8519	$190.85	$190.85	$190.90
Purchase #7	$40.91	9.719%	$44.886	$44.89	$44.90	$44.90
7 purchase totals =	$1,105.77		$1,210.3782	$1,210.39	$1,210.40	$1,210.50