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	$235.86	4.594%	$246.6954	$246.70	$246.70	$246.70
Purchase #2	$153.26	5.810%	$162.1644	$162.16	$162.15	$162.20
Purchase #3	$73.81	5.534%	$77.8946	$77.89	$77.90	$77.90
Purchase #4	$59.31	11.128%	$65.91	$65.91	$65.90	$65.90
Purchase #5	$185.88	5.233%	$195.6071	$195.61	$195.60	$195.60
Purchase #6	$218.43	10.710%	$241.8239	$241.82	$241.80	$241.80
Purchase #7	$77.97	9.728%	$85.5549	$85.55	$85.55	$85.60
7 purchase totals =	$1,004.52		$1,075.6503	$1,075.64	$1,075.60	$1,075.70