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	$111.50	11.630%	$124.4675	$124.47	$124.45	$124.50
Purchase #2	$172.80	11.781%	$193.1576	$193.16	$193.15	$193.20
Purchase #3	$68.98	4.112%	$71.8165	$71.82	$71.80	$71.80
Purchase #4	$14.83	7.418%	$15.9301	$15.93	$15.95	$15.90
Purchase #5	$176.67	13.409%	$200.3597	$200.36	$200.35	$200.40
Purchase #6	$166.96	3.157%	$172.2309	$172.23	$172.25	$172.20
Purchase #7	$188.64	9.167%	$205.9326	$205.93	$205.95	$205.90
7 purchase totals =	$900.38		$983.8949	$983.90	$983.90	$983.90