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	$68.46	5.283%	$72.0767	$72.08	$72.10	$72.10
Purchase #2	$32.68	6.673%	$34.8607	$34.86	$34.85	$34.90
Purchase #3	$144.51	5.105%	$151.8872	$151.89	$151.90	$151.90
Purchase #4	$11.26	8.756%	$12.2459	$12.25	$12.25	$12.20
Purchase #5	$35.87	6.703%	$38.2744	$38.27	$38.25	$38.30
Purchase #6	$205.57	13.112%	$232.5243	$232.52	$232.50	$232.50
Purchase #7	$139.69	5.142%	$146.8729	$146.87	$146.85	$146.90
7 purchase totals =	$638.04		$688.7421	$688.74	$688.70	$688.80