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	$10.25	5.681%	$10.8323	$10.83	$10.85	$10.80
Purchase #2	$6.83	11.116%	$7.5892	$7.59	$7.60	$7.60
Purchase #3	$76.72	11.469%	$85.519	$85.52	$85.50	$85.50
Purchase #4	$101.33	3.845%	$105.2261	$105.23	$105.25	$105.20
Purchase #5	$7.64	5.650%	$8.0717	$8.07	$8.05	$8.10
Purchase #6	$41.40	12.541%	$46.592	$46.59	$46.60	$46.60
Purchase #7	$52.77	5.535%	$55.6908	$55.69	$55.70	$55.70
7 purchase totals =	$296.94		$319.5211	$319.52	$319.55	$319.50