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	$100.97	9.608%	$110.6712	$110.67	$110.65	$110.70
Purchase #2	$33.27	13.249%	$37.6779	$37.68	$37.70	$37.70
Purchase #3	$246.51	12.706%	$277.8316	$277.83	$277.85	$277.80
Purchase #4	$62.27	8.255%	$67.4104	$67.41	$67.40	$67.40
Purchase #5	$44.92	12.845%	$50.69	$50.69	$50.70	$50.70
Purchase #6	$227.63	12.485%	$256.0496	$256.05	$256.05	$256.00
Purchase #7	$90.47	11.429%	$100.8098	$100.81	$100.80	$100.80
7 purchase totals =	$806.04		$901.1405	$901.14	$901.15	$901.10