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	$130.53	8.457%	$141.5689	$141.57	$141.55	$141.60
Purchase #2	$117.71	10.247%	$129.7717	$129.77	$129.75	$129.80
Purchase #3	$19.25	8.102%	$20.8096	$20.81	$20.80	$20.80
Purchase #4	$143.52	10.390%	$158.4317	$158.43	$158.45	$158.40
Purchase #5	$124.81	10.111%	$137.4295	$137.43	$137.45	$137.40
Purchase #6	$238.59	7.304%	$256.0166	$256.02	$256.00	$256.00
Purchase #7	$145.39	13.476%	$164.9828	$164.98	$165.00	$165.00
7 purchase totals =	$919.80		$1,009.0108	$1,009.01	$1,009.00	$1,009.00