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	$146.52	9.418%	$160.3193	$160.32	$160.30	$160.30
Purchase #2	$245.87	12.447%	$276.4734	$276.47	$276.45	$276.50
Purchase #3	$34.92	7.211%	$37.4381	$37.44	$37.45	$37.40
Purchase #4	$229.46	12.379%	$257.8649	$257.86	$257.85	$257.90
Purchase #5	$85.50	4.685%	$89.5057	$89.51	$89.50	$89.50
Purchase #6	$148.65	10.214%	$163.8331	$163.83	$163.85	$163.80
Purchase #7	$164.81	9.349%	$180.2181	$180.22	$180.20	$180.20
7 purchase totals =	$1,055.73		$1,165.6526	$1,165.65	$1,165.60	$1,165.60