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	$135.70	11.170%	$150.8577	$150.86	$150.85	$150.90
Purchase #2	$74.25	11.472%	$82.768	$82.77	$82.75	$82.80
Purchase #3	$41.28	6.126%	$43.8088	$43.81	$43.80	$43.80
Purchase #4	$87.37	3.493%	$90.4218	$90.42	$90.40	$90.40
Purchase #5	$112.41	6.295%	$119.4862	$119.49	$119.50	$119.50
Purchase #6	$122.30	7.316%	$131.2475	$131.25	$131.25	$131.20
Purchase #7	$129.42	6.190%	$137.4311	$137.43	$137.45	$137.40
7 purchase totals =	$702.73		$756.0211	$756.03	$756.00	$756.00