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	$155.56	12.532%	$175.0548	$175.05	$175.05	$175.10
Purchase #2	$194.83	6.705%	$207.8934	$207.89	$207.90	$207.90
Purchase #3	$157.44	3.286%	$162.6135	$162.61	$162.60	$162.60
Purchase #4	$38.77	12.823%	$43.7415	$43.74	$43.75	$43.70
Purchase #5	$145.59	6.527%	$155.0927	$155.09	$155.10	$155.10
Purchase #6	$168.28	13.201%	$190.4946	$190.49	$190.50	$190.50
Purchase #7	$58.66	6.630%	$62.5492	$62.55	$62.55	$62.50
7 purchase totals =	$919.13		$997.4397	$997.42	$997.45	$997.40