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	$39.57	8.867%	$43.0787	$43.08	$43.10	$43.10
Purchase #2	$129.46	7.500%	$139.1695	$139.17	$139.15	$139.20
Purchase #3	$204.58	10.449%	$225.9566	$225.96	$225.95	$226.00
Purchase #4	$163.42	7.725%	$176.0442	$176.04	$176.05	$176.00
Purchase #5	$40.92	6.412%	$43.5438	$43.54	$43.55	$43.50
Purchase #6	$155.29	11.107%	$172.5381	$172.54	$172.55	$172.50
Purchase #7	$237.45	6.572%	$253.0552	$253.06	$253.05	$253.10
7 purchase totals =	$970.69		$1,053.3861	$1,053.39	$1,053.40	$1,053.40