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	$127.88	10.126%	$140.8291	$140.83	$140.85	$140.80
Purchase #2	$138.45	12.365%	$155.5693	$155.57	$155.55	$155.60
Purchase #3	$41.88	7.107%	$44.8564	$44.86	$44.85	$44.90
Purchase #4	$176.80	5.605%	$186.7096	$186.71	$186.70	$186.70
Purchase #5	$233.80	3.116%	$241.0852	$241.09	$241.10	$241.10
Purchase #6	$53.59	6.504%	$57.0755	$57.08	$57.10	$57.10
Purchase #7	$241.89	11.321%	$269.2744	$269.27	$269.25	$269.30
7 purchase totals =	$1,014.29		$1,095.3995	$1,095.41	$1,095.40	$1,095.50