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	$213.29	9.359%	$233.2518	$233.25	$233.25	$233.30
Purchase #2	$15.27	10.342%	$16.8492	$16.85	$16.85	$16.80
Purchase #3	$79.80	11.641%	$89.0895	$89.09	$89.10	$89.10
Purchase #4	$14.63	3.198%	$15.0979	$15.10	$15.10	$15.10
Purchase #5	$176.78	7.491%	$190.0226	$190.02	$190.00	$190.00
Purchase #6	$164.37	9.328%	$179.7024	$179.70	$179.70	$179.70
Purchase #7	$69.94	11.708%	$78.1286	$78.13	$78.15	$78.10
7 purchase totals =	$734.08		$802.1420	$802.14	$802.15	$802.10