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	$148.83	13.219%	$168.5038	$168.50	$168.50	$168.50
Purchase #2	$13.77	3.747%	$14.286	$14.29	$14.30	$14.30
Purchase #3	$244.83	5.295%	$257.7937	$257.79	$257.80	$257.80
Purchase #4	$119.30	8.868%	$129.8795	$129.88	$129.90	$129.90
Purchase #5	$94.48	6.821%	$100.9245	$100.92	$100.90	$100.90
Purchase #6	$135.51	12.269%	$152.1357	$152.14	$152.15	$152.10
Purchase #7	$39.74	5.863%	$42.07	$42.07	$42.05	$42.10
7 purchase totals =	$796.46		$865.5932	$865.59	$865.60	$865.60