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	$58.89	11.364%	$65.5823	$65.58	$65.60	$65.60
Purchase #2	$21.42	3.431%	$22.1549	$22.15	$22.15	$22.20
Purchase #3	$168.65	4.358%	$175.9998	$176.00	$176.00	$176.00
Purchase #4	$121.86	12.692%	$137.3265	$137.33	$137.35	$137.30
Purchase #5	$7.91	6.110%	$8.3933	$8.39	$8.40	$8.40
Purchase #6	$98.88	13.864%	$112.5887	$112.59	$112.60	$112.60
Purchase #7	$71.42	9.364%	$78.1078	$78.11	$78.10	$78.10
7 purchase totals =	$549.03		$600.1533	$600.15	$600.20	$600.20