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	$158.27	5.257%	$166.5903	$166.59	$166.60	$166.60
Purchase #2	$164.36	8.600%	$178.495	$178.50	$178.50	$178.50
Purchase #3	$56.62	9.500%	$61.9989	$62.00	$62.00	$62.00
Purchase #4	$90.89	12.657%	$102.3939	$102.39	$102.40	$102.40
Purchase #5	$163.77	11.838%	$183.1571	$183.16	$183.15	$183.20
Purchase #6	$146.33	9.668%	$160.4772	$160.48	$160.50	$160.50
Purchase #7	$111.57	12.245%	$125.2317	$125.23	$125.25	$125.20
7 purchase totals =	$891.81		$978.3441	$978.35	$978.40	$978.40