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	$164.31	9.837%	$180.4732	$180.47	$180.45	$180.50
Purchase #2	$140.76	3.665%	$145.9189	$145.92	$145.90	$145.90
Purchase #3	$32.59	4.265%	$33.98	$33.98	$34.00	$34.00
Purchase #4	$66.51	5.329%	$70.0543	$70.05	$70.05	$70.10
Purchase #5	$242.92	12.150%	$272.4348	$272.43	$272.45	$272.40
Purchase #6	$185.43	4.228%	$193.27	$193.27	$193.25	$193.30
Purchase #7	$204.62	8.719%	$222.4608	$222.46	$222.45	$222.50
7 purchase totals =	$1,037.14		$1,118.5920	$1,118.58	$1,118.55	$1,118.70