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	$141.71	10.627%	$156.7695	$156.77	$156.75	$156.80
Purchase #2	$206.80	7.496%	$222.3017	$222.30	$222.30	$222.30
Purchase #3	$34.54	13.620%	$39.2443	$39.24	$39.25	$39.20
Purchase #4	$10.82	6.654%	$11.54	$11.54	$11.55	$11.50
Purchase #5	$25.70	5.574%	$27.1325	$27.13	$27.15	$27.10
Purchase #6	$147.98	7.231%	$158.6804	$158.68	$158.70	$158.70
Purchase #7	$152.34	12.293%	$171.0672	$171.07	$171.05	$171.10
7 purchase totals =	$719.89		$786.7356	$786.73	$786.75	$786.70