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	$13.95	13.793%	$15.8741	$15.87	$15.85	$15.90
Purchase #2	$157.41	10.174%	$173.4249	$173.42	$173.40	$173.40
Purchase #3	$19.59	7.315%	$21.023	$21.02	$21.00	$21.00
Purchase #4	$142.83	5.650%	$150.8999	$150.90	$150.90	$150.90
Purchase #5	$14.49	9.593%	$15.88	$15.88	$15.90	$15.90
Purchase #6	$92.36	13.244%	$104.5922	$104.59	$104.60	$104.60
Purchase #7	$241.88	11.776%	$270.3638	$270.36	$270.35	$270.40
7 purchase totals =	$682.51		$752.0579	$752.04	$752.00	$752.10