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	$86.72	9.115%	$94.6245	$94.62	$94.60	$94.60
Purchase #2	$152.55	9.166%	$166.5327	$166.53	$166.55	$166.50
Purchase #3	$55.45	3.504%	$57.393	$57.39	$57.40	$57.40
Purchase #4	$32.43	7.859%	$34.9787	$34.98	$35.00	$35.00
Purchase #5	$12.85	4.163%	$13.3849	$13.38	$13.40	$13.40
Purchase #6	$148.69	5.407%	$156.7297	$156.73	$156.75	$156.70
Purchase #7	$161.34	7.492%	$173.4276	$173.43	$173.45	$173.40
7 purchase totals =	$650.03		$697.0711	$697.06	$697.15	$697.00