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	$43.33	5.434%	$45.6846	$45.68	$45.70	$45.70
Purchase #2	$215.52	8.490%	$233.8176	$233.82	$233.80	$233.80
Purchase #3	$124.34	10.576%	$137.4902	$137.49	$137.50	$137.50
Purchase #4	$190.78	8.729%	$207.4332	$207.43	$207.45	$207.40
Purchase #5	$124.53	10.485%	$137.587	$137.59	$137.60	$137.60
Purchase #6	$80.97	10.217%	$89.2427	$89.24	$89.25	$89.20
Purchase #7	$209.39	11.716%	$233.9221	$233.92	$233.90	$233.90
7 purchase totals =	$988.86		$1,085.1774	$1,085.17	$1,085.20	$1,085.10