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	$153.79	13.753%	$174.9407	$174.94	$174.95	$174.90
Purchase #2	$34.73	9.234%	$37.937	$37.94	$37.95	$37.90
Purchase #3	$40.34	3.540%	$41.768	$41.77	$41.75	$41.80
Purchase #4	$10.96	12.849%	$12.3683	$12.37	$12.35	$12.40
Purchase #5	$151.25	6.583%	$161.2068	$161.21	$161.20	$161.20
Purchase #6	$113.32	12.233%	$127.1824	$127.18	$127.20	$127.20
Purchase #7	$64.32	4.710%	$67.3495	$67.35	$67.35	$67.30
7 purchase totals =	$568.71		$622.7527	$622.76	$622.75	$622.70