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	$95.54	13.652%	$108.5831	$108.58	$108.60	$108.60
Purchase #2	$174.59	12.586%	$196.5639	$196.56	$196.55	$196.60
Purchase #3	$153.93	12.634%	$173.3775	$173.38	$173.40	$173.40
Purchase #4	$32.74	7.831%	$35.3039	$35.30	$35.30	$35.30
Purchase #5	$86.46	8.452%	$93.7676	$93.77	$93.75	$93.80
Purchase #6	$196.49	4.745%	$205.8135	$205.81	$205.80	$205.80
Purchase #7	$49.29	13.303%	$55.847	$55.85	$55.85	$55.80
7 purchase totals =	$789.04		$869.2565	$869.25	$869.25	$869.30