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	$142.55	13.141%	$161.2825	$161.28	$161.30	$161.30
Purchase #2	$240.61	3.548%	$249.1468	$249.15	$249.15	$249.10
Purchase #3	$188.60	10.760%	$208.8934	$208.89	$208.90	$208.90
Purchase #4	$14.69	4.608%	$15.3669	$15.37	$15.35	$15.40
Purchase #5	$108.25	10.788%	$119.928	$119.93	$119.95	$119.90
Purchase #6	$98.28	11.862%	$109.938	$109.94	$109.95	$109.90
Purchase #7	$91.96	9.126%	$100.3523	$100.35	$100.35	$100.40
7 purchase totals =	$884.94		$964.9079	$964.91	$964.95	$964.90