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	$146.31	3.451%	$151.3592	$151.36	$151.35	$151.40
Purchase #2	$52.65	13.839%	$59.9362	$59.94	$59.95	$59.90
Purchase #3	$142.72	7.385%	$153.2599	$153.26	$153.25	$153.30
Purchase #4	$187.96	13.244%	$212.8534	$212.85	$212.85	$212.90
Purchase #5	$77.55	3.442%	$80.2193	$80.22	$80.20	$80.20
Purchase #6	$145.75	12.649%	$164.1859	$164.19	$164.20	$164.20
Purchase #7	$51.60	5.397%	$54.3849	$54.38	$54.40	$54.40
7 purchase totals =	$804.54		$876.1988	$876.20	$876.20	$876.30