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	$84.81	7.485%	$91.158	$91.16	$91.15	$91.20
Purchase #2	$45.58	11.499%	$50.8212	$50.82	$50.80	$50.80
Purchase #3	$95.97	4.605%	$100.3894	$100.39	$100.40	$100.40
Purchase #4	$241.29	3.389%	$249.4673	$249.47	$249.45	$249.50
Purchase #5	$105.29	13.287%	$119.2799	$119.28	$119.30	$119.30
Purchase #6	$12.63	6.218%	$13.4153	$13.42	$13.40	$13.40
Purchase #7	$112.83	13.772%	$128.3689	$128.37	$128.35	$128.40
7 purchase totals =	$698.40		$752.9000	$752.91	$752.85	$753.00