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	$244.81	8.744%	$266.2162	$266.22	$266.20	$266.20
Purchase #2	$139.70	4.815%	$146.4266	$146.43	$146.45	$146.40
Purchase #3	$40.57	4.461%	$42.3798	$42.38	$42.40	$42.40
Purchase #4	$55.25	6.832%	$59.0247	$59.02	$59.00	$59.00
Purchase #5	$190.52	6.329%	$202.578	$202.58	$202.60	$202.60
Purchase #6	$42.77	3.454%	$44.2473	$44.25	$44.25	$44.20
Purchase #7	$10.89	5.543%	$11.4936	$11.49	$11.50	$11.50
7 purchase totals =	$724.51		$772.3662	$772.37	$772.40	$772.30