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	$105.49	5.432%	$111.2202	$111.22	$111.20	$111.20
Purchase #2	$228.93	3.326%	$236.5442	$236.54	$236.55	$236.50
Purchase #3	$27.54	13.795%	$31.3391	$31.34	$31.35	$31.30
Purchase #4	$66.88	7.458%	$71.8679	$71.87	$71.85	$71.90
Purchase #5	$141.69	6.292%	$150.6051	$150.61	$150.60	$150.60
Purchase #6	$124.54	8.102%	$134.6302	$134.63	$134.65	$134.60
Purchase #7	$153.45	9.394%	$167.8651	$167.87	$167.85	$167.90
7 purchase totals =	$848.52		$904.0718	$904.08	$904.05	$904.00