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	$77.31	11.554%	$86.2424	$86.24	$86.25	$86.20
Purchase #2	$191.61	7.132%	$205.2756	$205.28	$205.30	$205.30
Purchase #3	$99.37	13.193%	$112.4799	$112.48	$112.50	$112.50
Purchase #4	$153.90	5.536%	$162.4199	$162.42	$162.40	$162.40
Purchase #5	$200.45	11.439%	$223.3795	$223.38	$223.40	$223.40
Purchase #6	$151.28	13.185%	$171.2263	$171.23	$171.25	$171.20
Purchase #7	$132.33	4.119%	$137.7807	$137.78	$137.80	$137.80
7 purchase totals =	$1,006.25		$1,098.8043	$1,098.81	$1,098.90	$1,098.80