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	$64.92	9.834%	$71.3042	$71.30	$71.30	$71.30
Purchase #2	$106.30	10.383%	$117.3371	$117.34	$117.35	$117.30
Purchase #3	$95.30	4.521%	$99.6085	$99.61	$99.60	$99.60
Purchase #4	$191.89	4.661%	$200.834	$200.83	$200.85	$200.80
Purchase #5	$243.79	3.438%	$252.1715	$252.17	$252.15	$252.20
Purchase #6	$124.79	6.477%	$132.8726	$132.87	$132.85	$132.90
Purchase #7	$237.25	8.856%	$258.2609	$258.26	$258.25	$258.30
7 purchase totals =	$1,064.24		$1,132.3888	$1,132.38	$1,132.35	$1,132.40