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	$156.85	13.521%	$178.0577	$178.06	$178.05	$178.10
Purchase #2	$108.51	4.366%	$113.2475	$113.25	$113.25	$113.20
Purchase #3	$208.88	13.244%	$236.5441	$236.54	$236.55	$236.50
Purchase #4	$158.56	7.766%	$170.8738	$170.87	$170.85	$170.90
Purchase #5	$99.39	5.792%	$105.1467	$105.15	$105.15	$105.10
Purchase #6	$102.79	13.588%	$116.7571	$116.76	$116.75	$116.80
Purchase #7	$218.77	10.273%	$241.2442	$241.24	$241.25	$241.20
7 purchase totals =	$1,053.75		$1,161.8711	$1,161.87	$1,161.85	$1,161.80