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	$177.72	4.410%	$185.5575	$185.56	$185.55	$185.60
Purchase #2	$233.98	9.584%	$256.4046	$256.40	$256.40	$256.40
Purchase #3	$171.76	3.777%	$178.2474	$178.25	$178.25	$178.20
Purchase #4	$95.58	8.760%	$103.9528	$103.95	$103.95	$104.00
Purchase #5	$197.61	12.292%	$221.9002	$221.90	$221.90	$221.90
Purchase #6	$40.89	8.751%	$44.4683	$44.47	$44.45	$44.50
Purchase #7	$157.88	10.596%	$174.609	$174.61	$174.60	$174.60
7 purchase totals =	$1,075.42		$1,165.1398	$1,165.14	$1,165.10	$1,165.20