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	$68.54	3.737%	$71.1013	$71.10	$71.10	$71.10
Purchase #2	$246.41	4.105%	$256.5251	$256.53	$256.55	$256.50
Purchase #3	$230.56	12.627%	$259.6728	$259.67	$259.65	$259.70
Purchase #4	$147.77	6.449%	$157.2997	$157.30	$157.30	$157.30
Purchase #5	$210.32	9.620%	$230.5528	$230.55	$230.55	$230.60
Purchase #6	$45.91	6.593%	$48.9368	$48.94	$48.95	$48.90
Purchase #7	$43.47	5.479%	$45.8517	$45.85	$45.85	$45.90
7 purchase totals =	$992.98		$1,069.9402	$1,069.94	$1,069.95	$1,070.00