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	$152.77	4.752%	$160.0296	$160.03	$160.05	$160.00
Purchase #2	$30.66	12.569%	$34.5137	$34.51	$34.50	$34.50
Purchase #3	$11.87	7.136%	$12.717	$12.72	$12.70	$12.70
Purchase #4	$170.65	8.677%	$185.4573	$185.46	$185.45	$185.50
Purchase #5	$116.61	13.706%	$132.5926	$132.59	$132.60	$132.60
Purchase #6	$32.47	10.454%	$35.8644	$35.86	$35.85	$35.90
Purchase #7	$129.45	13.183%	$146.5154	$146.52	$146.50	$146.50
7 purchase totals =	$644.48		$707.6900	$707.69	$707.65	$707.70