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	$40.94	9.146%	$44.6844	$44.68	$44.70	$44.70
Purchase #2	$164.25	4.631%	$171.8564	$171.86	$171.85	$171.90
Purchase #3	$52.44	13.680%	$59.6138	$59.61	$59.60	$59.60
Purchase #4	$27.32	5.489%	$28.8196	$28.82	$28.80	$28.80
Purchase #5	$172.44	5.848%	$182.5243	$182.52	$182.50	$182.50
Purchase #6	$246.71	9.366%	$269.8169	$269.82	$269.80	$269.80
Purchase #7	$187.77	11.708%	$209.7541	$209.75	$209.75	$209.80
7 purchase totals =	$891.87		$967.0695	$967.06	$967.00	$967.10