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	$143.80	8.331%	$155.78	$155.78	$155.80	$155.80
Purchase #2	$50.75	5.426%	$53.5037	$53.50	$53.50	$53.50
Purchase #3	$111.36	11.696%	$124.3847	$124.38	$124.40	$124.40
Purchase #4	$202.96	3.862%	$210.7983	$210.80	$210.80	$210.80
Purchase #5	$100.47	3.464%	$103.9503	$103.95	$103.95	$104.00
Purchase #6	$180.96	5.108%	$190.2034	$190.20	$190.20	$190.20
Purchase #7	$121.26	13.748%	$137.9308	$137.93	$137.95	$137.90
7 purchase totals =	$911.56		$976.5512	$976.54	$976.60	$976.60