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	$184.86	6.265%	$196.4415	$196.44	$196.45	$196.40
Purchase #2	$199.38	8.625%	$216.5765	$216.58	$216.60	$216.60
Purchase #3	$214.61	10.683%	$237.5368	$237.54	$237.55	$237.50
Purchase #4	$40.65	12.374%	$45.68	$45.68	$45.70	$45.70
Purchase #5	$148.34	6.650%	$158.2046	$158.20	$158.20	$158.20
Purchase #6	$48.94	5.514%	$51.6386	$51.64	$51.65	$51.60
Purchase #7	$222.32	7.389%	$238.7472	$238.75	$238.75	$238.70
7 purchase totals =	$1,059.10		$1,144.8252	$1,144.83	$1,144.90	$1,144.70