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	$224.52	8.662%	$243.9679	$243.97	$243.95	$244.00
Purchase #2	$56.85	10.691%	$62.9278	$62.93	$62.95	$62.90
Purchase #3	$32.58	9.663%	$35.7282	$35.73	$35.75	$35.70
Purchase #4	$119.34	6.806%	$127.4623	$127.46	$127.45	$127.50
Purchase #5	$217.85	13.160%	$246.5191	$246.52	$246.50	$246.50
Purchase #6	$65.44	10.606%	$72.3806	$72.38	$72.40	$72.40
Purchase #7	$40.42	4.603%	$42.2805	$42.28	$42.30	$42.30
7 purchase totals =	$757.00		$831.2664	$831.27	$831.30	$831.30