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	$72.48	6.345%	$77.0789	$77.08	$77.10	$77.10
Purchase #2	$12.31	10.598%	$13.6146	$13.61	$13.60	$13.60
Purchase #3	$85.47	12.479%	$96.1358	$96.14	$96.15	$96.10
Purchase #4	$77.98	7.314%	$83.6835	$83.68	$83.70	$83.70
Purchase #5	$64.82	3.179%	$66.8806	$66.88	$66.90	$66.90
Purchase #6	$130.29	11.239%	$144.9333	$144.93	$144.95	$144.90
Purchase #7	$182.82	13.823%	$208.0912	$208.09	$208.10	$208.10
7 purchase totals =	$626.17		$690.4179	$690.41	$690.50	$690.40