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	$63.97	11.599%	$71.3899	$71.39	$71.40	$71.40
Purchase #2	$64.77	5.104%	$68.0759	$68.08	$68.10	$68.10
Purchase #3	$249.83	11.873%	$279.4923	$279.49	$279.50	$279.50
Purchase #4	$47.90	12.619%	$53.9445	$53.94	$53.95	$53.90
Purchase #5	$230.29	10.799%	$255.159	$255.16	$255.15	$255.20
Purchase #6	$133.81	3.253%	$138.1628	$138.16	$138.15	$138.20
Purchase #7	$52.32	8.231%	$56.6265	$56.63	$56.65	$56.60
7 purchase totals =	$842.89		$922.8509	$922.85	$922.90	$922.90