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	$164.28	4.327%	$171.3884	$171.39	$171.40	$171.40
Purchase #2	$90.86	5.633%	$95.9781	$95.98	$96.00	$96.00
Purchase #3	$189.91	5.423%	$200.2088	$200.21	$200.20	$200.20
Purchase #4	$140.32	4.320%	$146.3818	$146.38	$146.40	$146.40
Purchase #5	$74.45	12.540%	$83.786	$83.79	$83.80	$83.80
Purchase #6	$11.94	13.173%	$13.5129	$13.51	$13.50	$13.50
Purchase #7	$106.95	10.850%	$118.5541	$118.55	$118.55	$118.60
7 purchase totals =	$778.71		$829.8101	$829.81	$829.85	$829.90