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	$53.69	11.279%	$59.7457	$59.75	$59.75	$59.70
Purchase #2	$49.64	4.105%	$51.6777	$51.68	$51.70	$51.70
Purchase #3	$113.29	6.604%	$120.7717	$120.77	$120.75	$120.80
Purchase #4	$50.34	12.149%	$56.4558	$56.46	$56.45	$56.50
Purchase #5	$20.55	11.401%	$22.8929	$22.89	$22.90	$22.90
Purchase #6	$239.62	6.667%	$255.5955	$255.60	$255.60	$255.60
Purchase #7	$52.31	12.751%	$58.98	$58.98	$59.00	$59.00
7 purchase totals =	$579.44		$626.1193	$626.13	$626.15	$626.20