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	$157.39	10.506%	$173.9254	$173.93	$173.95	$173.90
Purchase #2	$20.95	3.593%	$21.7027	$21.70	$21.70	$21.70
Purchase #3	$132.72	11.527%	$148.0186	$148.02	$148.00	$148.00
Purchase #4	$57.49	3.637%	$59.5809	$59.58	$59.60	$59.60
Purchase #5	$224.78	13.699%	$255.5726	$255.57	$255.55	$255.60
Purchase #6	$230.78	6.625%	$246.0692	$246.07	$246.05	$246.10
Purchase #7	$109.57	6.383%	$116.5639	$116.56	$116.55	$116.60
7 purchase totals =	$933.68		$1,021.4333	$1,021.43	$1,021.40	$1,021.50