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	$35.32	4.375%	$36.8653	$36.87	$36.85	$36.90
Purchase #2	$77.40	12.178%	$86.8258	$86.83	$86.85	$86.80
Purchase #3	$162.32	10.293%	$179.0276	$179.03	$179.05	$179.00
Purchase #4	$83.70	7.714%	$90.1566	$90.16	$90.15	$90.20
Purchase #5	$155.86	9.497%	$170.662	$170.66	$170.65	$170.70
Purchase #6	$15.33	7.483%	$16.4771	$16.48	$16.50	$16.50
Purchase #7	$150.83	5.125%	$158.56	$158.56	$158.55	$158.60
7 purchase totals =	$680.76		$738.5744	$738.59	$738.60	$738.70