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	$63.69	6.243%	$67.6662	$67.67	$67.65	$67.70
Purchase #2	$9.67	6.429%	$10.2917	$10.29	$10.30	$10.30
Purchase #3	$55.25	7.317%	$59.2926	$59.29	$59.30	$59.30
Purchase #4	$16.27	7.542%	$17.4971	$17.50	$17.50	$17.50
Purchase #5	$130.96	4.122%	$136.3582	$136.36	$136.35	$136.40
Purchase #6	$191.27	11.151%	$212.5985	$212.60	$212.60	$212.60
Purchase #7	$61.41	5.105%	$64.545	$64.55	$64.55	$64.50
7 purchase totals =	$528.52		$568.2493	$568.26	$568.25	$568.30