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	$62.89	3.530%	$65.11	$65.11	$65.10	$65.10
Purchase #2	$224.33	12.335%	$252.0011	$252.00	$252.00	$252.00
Purchase #3	$98.85	13.861%	$112.5516	$112.55	$112.55	$112.60
Purchase #4	$126.72	12.674%	$142.7805	$142.78	$142.80	$142.80
Purchase #5	$76.57	4.381%	$79.9245	$79.92	$79.90	$79.90
Purchase #6	$188.60	3.166%	$194.5711	$194.57	$194.55	$194.60
Purchase #7	$81.95	10.465%	$90.5261	$90.53	$90.55	$90.50
7 purchase totals =	$859.91		$937.4649	$937.46	$937.45	$937.50