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	$228.45	7.681%	$245.9972	$246.00	$246.00	$246.00
Purchase #2	$43.85	10.134%	$48.2938	$48.29	$48.30	$48.30
Purchase #3	$12.80	5.382%	$13.4889	$13.49	$13.50	$13.50
Purchase #4	$157.49	6.111%	$167.1142	$167.11	$167.10	$167.10
Purchase #5	$188.74	11.115%	$209.7185	$209.72	$209.70	$209.70
Purchase #6	$133.68	4.190%	$139.2812	$139.28	$139.30	$139.30
Purchase #7	$225.65	13.721%	$256.6114	$256.61	$256.60	$256.60
7 purchase totals =	$990.66		$1,080.5052	$1,080.50	$1,080.50	$1,080.50