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	$130.34	11.182%	$144.9146	$144.91	$144.90	$144.90
Purchase #2	$198.73	7.703%	$214.0382	$214.04	$214.05	$214.00
Purchase #3	$146.34	12.475%	$164.5959	$164.60	$164.60	$164.60
Purchase #4	$85.52	5.616%	$90.3228	$90.32	$90.30	$90.30
Purchase #5	$81.51	5.816%	$86.2506	$86.25	$86.25	$86.30
Purchase #6	$147.72	13.184%	$167.1954	$167.20	$167.20	$167.20
Purchase #7	$80.76	3.795%	$83.8248	$83.82	$83.80	$83.80
7 purchase totals =	$870.92		$951.1423	$951.14	$951.10	$951.10