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	$30.74	10.169%	$33.866	$33.87	$33.85	$33.90
Purchase #2	$24.55	13.297%	$27.8144	$27.81	$27.80	$27.80
Purchase #3	$159.71	5.306%	$168.1842	$168.18	$168.20	$168.20
Purchase #4	$31.25	9.517%	$34.2241	$34.22	$34.20	$34.20
Purchase #5	$67.94	4.807%	$71.2059	$71.21	$71.20	$71.20
Purchase #6	$33.42	12.473%	$37.5885	$37.59	$37.60	$37.60
Purchase #7	$12.46	12.705%	$14.043	$14.04	$14.05	$14.00
7 purchase totals =	$360.07		$386.9261	$386.92	$386.90	$386.90