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	$153.59	8.102%	$166.0339	$166.03	$166.05	$166.00
Purchase #2	$42.63	13.713%	$48.4759	$48.48	$48.50	$48.50
Purchase #3	$82.61	5.109%	$86.8305	$86.83	$86.85	$86.80
Purchase #4	$132.34	3.232%	$136.6172	$136.62	$136.60	$136.60
Purchase #5	$59.64	8.569%	$64.7506	$64.75	$64.75	$64.80
Purchase #6	$43.79	10.680%	$48.4668	$48.47	$48.45	$48.50
Purchase #7	$142.32	7.406%	$152.8602	$152.86	$152.85	$152.90
7 purchase totals =	$656.92		$704.0351	$704.04	$704.05	$704.10