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	$134.52	7.792%	$145.0018	$145.00	$145.00	$145.00
Purchase #2	$152.72	7.482%	$164.1465	$164.15	$164.15	$164.10
Purchase #3	$199.89	7.284%	$214.45	$214.45	$214.45	$214.50
Purchase #4	$177.29	5.239%	$186.5782	$186.58	$186.60	$186.60
Purchase #5	$77.29	10.316%	$85.2632	$85.26	$85.25	$85.30
Purchase #6	$180.29	12.844%	$203.4464	$203.45	$203.45	$203.40
Purchase #7	$167.39	13.663%	$190.2605	$190.26	$190.25	$190.30
7 purchase totals =	$1,089.39		$1,189.1466	$1,189.15	$1,189.15	$1,189.20