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	$246.60	5.601%	$260.4121	$260.41	$260.40	$260.40
Purchase #2	$99.53	6.108%	$105.6093	$105.61	$105.60	$105.60
Purchase #3	$181.58	9.141%	$198.1782	$198.18	$198.20	$198.20
Purchase #4	$36.55	4.349%	$38.1396	$38.14	$38.15	$38.10
Purchase #5	$37.49	7.814%	$40.4195	$40.42	$40.40	$40.40
Purchase #6	$10.59	6.493%	$11.2776	$11.28	$11.30	$11.30
Purchase #7	$125.81	13.643%	$142.9743	$142.97	$142.95	$143.00
7 purchase totals =	$738.15		$797.0106	$797.01	$797.00	$797.00