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	$241.99	11.468%	$269.7414	$269.74	$269.75	$269.70
Purchase #2	$68.97	5.683%	$72.8896	$72.89	$72.90	$72.90
Purchase #3	$36.26	4.585%	$37.9225	$37.92	$37.90	$37.90
Purchase #4	$112.60	11.469%	$125.5141	$125.51	$125.50	$125.50
Purchase #5	$81.25	13.548%	$92.2578	$92.26	$92.25	$92.30
Purchase #6	$37.96	13.367%	$43.0341	$43.03	$43.05	$43.00
Purchase #7	$47.85	10.542%	$52.8943	$52.89	$52.90	$52.90
7 purchase totals =	$626.88		$694.2538	$694.24	$694.25	$694.20