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	$156.38	7.198%	$167.6362	$167.64	$167.65	$167.60
Purchase #2	$221.78	8.788%	$241.27	$241.27	$241.25	$241.30
Purchase #3	$73.31	5.726%	$77.5077	$77.51	$77.50	$77.50
Purchase #4	$87.75	10.131%	$96.64	$96.64	$96.65	$96.60
Purchase #5	$239.80	8.248%	$259.5787	$259.58	$259.60	$259.60
Purchase #6	$53.32	10.607%	$58.9757	$58.98	$59.00	$59.00
Purchase #7	$142.75	7.494%	$153.4477	$153.45	$153.45	$153.40
7 purchase totals =	$975.09		$1,055.0560	$1,055.07	$1,055.10	$1,055.00