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	$56.50	6.499%	$60.1719	$60.17	$60.15	$60.20
Purchase #2	$208.81	4.516%	$218.2399	$218.24	$218.25	$218.20
Purchase #3	$246.60	3.162%	$254.3975	$254.40	$254.40	$254.40
Purchase #4	$95.92	13.196%	$108.5776	$108.58	$108.60	$108.60
Purchase #5	$76.83	7.149%	$82.3226	$82.32	$82.30	$82.30
Purchase #6	$97.88	6.838%	$104.573	$104.57	$104.55	$104.60
Purchase #7	$54.73	5.160%	$57.5541	$57.55	$57.55	$57.60
7 purchase totals =	$837.27		$885.8366	$885.83	$885.80	$885.90