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	$150.58	7.534%	$161.9247	$161.92	$161.90	$161.90
Purchase #2	$5.60	4.412%	$5.8471	$5.85	$5.85	$5.80
Purchase #3	$177.39	5.748%	$187.5864	$187.59	$187.60	$187.60
Purchase #4	$37.82	12.659%	$42.6076	$42.61	$42.60	$42.60
Purchase #5	$67.71	6.340%	$72.0028	$72.00	$72.00	$72.00
Purchase #6	$232.95	9.142%	$254.2463	$254.25	$254.25	$254.20
Purchase #7	$38.93	3.677%	$40.3615	$40.36	$40.35	$40.40
7 purchase totals =	$710.98		$764.5764	$764.58	$764.55	$764.50