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	$111.59	10.636%	$123.4587	$123.46	$123.45	$123.50
Purchase #2	$123.59	6.403%	$131.5035	$131.50	$131.50	$131.50
Purchase #3	$183.28	5.493%	$193.3476	$193.35	$193.35	$193.30
Purchase #4	$127.28	3.462%	$131.6864	$131.69	$131.70	$131.70
Purchase #5	$115.81	10.645%	$128.138	$128.14	$128.15	$128.10
Purchase #6	$239.36	8.704%	$260.1939	$260.19	$260.20	$260.20
Purchase #7	$230.29	11.220%	$256.1285	$256.13	$256.15	$256.10
7 purchase totals =	$1,131.20		$1,224.4566	$1,224.46	$1,224.50	$1,224.40