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	$143.53	10.649%	$158.8145	$158.81	$158.80	$158.80
Purchase #2	$232.63	10.235%	$256.4397	$256.44	$256.45	$256.40
Purchase #3	$222.83	6.330%	$236.9351	$236.94	$236.95	$236.90
Purchase #4	$177.54	6.240%	$188.6185	$188.62	$188.60	$188.60
Purchase #5	$36.38	12.637%	$40.9773	$40.98	$41.00	$41.00
Purchase #6	$18.36	10.255%	$20.2428	$20.24	$20.25	$20.20
Purchase #7	$219.30	10.127%	$241.5085	$241.51	$241.50	$241.50
7 purchase totals =	$1,050.57		$1,143.5364	$1,143.54	$1,143.55	$1,143.40