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	$249.39	10.203%	$274.8353	$274.84	$274.85	$274.80
Purchase #2	$95.39	10.372%	$105.2839	$105.28	$105.30	$105.30
Purchase #3	$213.29	7.390%	$229.0521	$229.05	$229.05	$229.10
Purchase #4	$112.62	13.599%	$127.9352	$127.94	$127.95	$127.90
Purchase #5	$152.80	6.669%	$162.9902	$162.99	$163.00	$163.00
Purchase #6	$102.61	8.834%	$111.6746	$111.67	$111.65	$111.70
Purchase #7	$125.75	11.548%	$140.2716	$140.27	$140.25	$140.30
7 purchase totals =	$1,051.85		$1,152.0429	$1,152.04	$1,152.05	$1,152.10