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	$115.36	9.410%	$126.2154	$126.22	$126.20	$126.20
Purchase #2	$77.59	10.309%	$85.5888	$85.59	$85.60	$85.60
Purchase #3	$11.98	3.348%	$12.3811	$12.38	$12.40	$12.40
Purchase #4	$234.97	12.602%	$264.5809	$264.58	$264.60	$264.60
Purchase #5	$189.88	13.477%	$215.4701	$215.47	$215.45	$215.50
Purchase #6	$201.29	5.609%	$212.5804	$212.58	$212.60	$212.60
Purchase #7	$68.56	5.484%	$72.3198	$72.32	$72.30	$72.30
7 purchase totals =	$899.63		$989.1365	$989.14	$989.15	$989.20