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	$87.87	8.474%	$95.3161	$95.32	$95.30	$95.30
Purchase #2	$38.42	9.517%	$42.0764	$42.08	$42.10	$42.10
Purchase #3	$147.92	8.564%	$160.5879	$160.59	$160.60	$160.60
Purchase #4	$230.96	3.125%	$238.1775	$238.18	$238.20	$238.20
Purchase #5	$236.62	9.815%	$259.8443	$259.84	$259.85	$259.80
Purchase #6	$54.82	8.757%	$59.6206	$59.62	$59.60	$59.60
Purchase #7	$140.85	7.179%	$150.9616	$150.96	$150.95	$151.00
7 purchase totals =	$937.46		$1,006.5844	$1,006.59	$1,006.60	$1,006.60