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	$229.58	6.753%	$245.0835	$245.08	$245.10	$245.10
Purchase #2	$35.70	5.533%	$37.6753	$37.68	$37.70	$37.70
Purchase #3	$127.58	8.620%	$138.5774	$138.58	$138.60	$138.60
Purchase #4	$94.99	5.762%	$100.4633	$100.46	$100.45	$100.50
Purchase #5	$247.25	13.188%	$279.8573	$279.86	$279.85	$279.90
Purchase #6	$35.38	3.462%	$36.6049	$36.60	$36.60	$36.60
Purchase #7	$193.59	13.359%	$219.4517	$219.45	$219.45	$219.50
7 purchase totals =	$964.07		$1,057.7134	$1,057.71	$1,057.75	$1,057.90