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	3.573%	$65.9656	$65.97	$65.95	$66.00
Purchase #2	$155.72	11.247%	$173.2338	$173.23	$173.25	$173.20
Purchase #3	$170.40	8.348%	$184.625	$184.63	$184.65	$184.60
Purchase #4	$188.55	4.449%	$196.9386	$196.94	$196.95	$196.90
Purchase #5	$148.87	12.335%	$167.2331	$167.23	$167.25	$167.20
Purchase #6	$12.56	6.700%	$13.4015	$13.40	$13.40	$13.40
Purchase #7	$76.83	6.820%	$82.0698	$82.07	$82.05	$82.10
7 purchase totals =	$816.62		$883.4674	$883.47	$883.50	$883.40