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	$31.35	8.554%	$34.0317	$34.03	$34.05	$34.00
Purchase #2	$126.96	13.464%	$144.0539	$144.05	$144.05	$144.10
Purchase #3	$50.52	9.208%	$55.1719	$55.17	$55.15	$55.20
Purchase #4	$74.31	6.206%	$78.9217	$78.92	$78.90	$78.90
Purchase #5	$105.60	3.585%	$109.3858	$109.39	$109.40	$109.40
Purchase #6	$243.75	9.687%	$267.3621	$267.36	$267.35	$267.40
Purchase #7	$36.86	3.357%	$38.0974	$38.10	$38.10	$38.10
7 purchase totals =	$669.35		$727.0245	$727.02	$727.00	$727.10