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	$32.93	12.663%	$37.0999	$37.10	$37.10	$37.10
Purchase #2	$129.91	7.186%	$139.2453	$139.25	$139.25	$139.20
Purchase #3	$38.79	7.257%	$41.605	$41.61	$41.60	$41.60
Purchase #4	$151.48	4.268%	$157.9452	$157.95	$157.95	$157.90
Purchase #5	$93.87	10.578%	$103.7996	$103.80	$103.80	$103.80
Purchase #6	$33.62	10.335%	$37.0946	$37.09	$37.10	$37.10
Purchase #7	$39.43	11.460%	$43.9487	$43.95	$43.95	$43.90
7 purchase totals =	$520.03		$560.7383	$560.75	$560.75	$560.60