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	$42.81	5.283%	$45.0717	$45.07	$45.05	$45.10
Purchase #2	$48.37	10.629%	$53.5112	$53.51	$53.50	$53.50
Purchase #3	$94.84	10.857%	$105.1368	$105.14	$105.15	$105.10
Purchase #4	$48.85	11.647%	$54.5396	$54.54	$54.55	$54.50
Purchase #5	$178.87	11.279%	$199.0447	$199.04	$199.05	$199.00
Purchase #6	$213.75	10.686%	$236.5913	$236.59	$236.60	$236.60
Purchase #7	$171.69	9.684%	$188.3165	$188.32	$188.30	$188.30
7 purchase totals =	$799.18		$882.2118	$882.21	$882.20	$882.10