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	$54.62	13.585%	$62.0401	$62.04	$62.05	$62.00
Purchase #2	$70.32	8.755%	$76.4765	$76.48	$76.50	$76.50
Purchase #3	$41.72	3.604%	$43.2236	$43.22	$43.20	$43.20
Purchase #4	$38.51	10.394%	$42.5127	$42.51	$42.50	$42.50
Purchase #5	$221.39	8.154%	$239.4421	$239.44	$239.45	$239.40
Purchase #6	$82.45	9.624%	$90.385	$90.39	$90.40	$90.40
Purchase #7	$12.47	9.699%	$13.6795	$13.68	$13.70	$13.70
7 purchase totals =	$521.48		$567.7595	$567.76	$567.80	$567.70