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	$33.91	9.245%	$37.045	$37.05	$37.05	$37.00
Purchase #2	$144.69	7.853%	$156.0525	$156.05	$156.05	$156.10
Purchase #3	$158.55	12.527%	$178.4116	$178.41	$178.40	$178.40
Purchase #4	$40.78	4.320%	$42.5417	$42.54	$42.55	$42.50
Purchase #5	$177.82	10.603%	$196.6743	$196.67	$196.65	$196.70
Purchase #6	$46.59	12.364%	$52.3504	$52.35	$52.35	$52.40
Purchase #7	$34.66	6.210%	$36.8124	$36.81	$36.80	$36.80
7 purchase totals =	$637.00		$699.8879	$699.88	$699.85	$699.90