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	$228.59	10.273%	$252.0731	$252.07	$252.05	$252.10
Purchase #2	$92.61	13.569%	$105.1763	$105.18	$105.20	$105.20
Purchase #3	$249.63	6.683%	$266.3128	$266.31	$266.30	$266.30
Purchase #4	$187.27	5.105%	$196.8301	$196.83	$196.85	$196.80
Purchase #5	$151.75	13.708%	$172.5519	$172.55	$172.55	$172.60
Purchase #6	$224.78	8.466%	$243.8099	$243.81	$243.80	$243.80
Purchase #7	$125.90	3.697%	$130.5545	$130.55	$130.55	$130.60
7 purchase totals =	$1,260.53		$1,367.3086	$1,367.30	$1,367.30	$1,367.40