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	$61.49	8.592%	$66.7732	$66.77	$66.75	$66.80
Purchase #2	$124.70	12.593%	$140.4035	$140.40	$140.40	$140.40
Purchase #3	$215.96	3.198%	$222.8664	$222.87	$222.85	$222.90
Purchase #4	$68.66	12.368%	$77.1519	$77.15	$77.15	$77.20
Purchase #5	$101.70	3.752%	$105.5158	$105.52	$105.50	$105.50
Purchase #6	$192.90	7.555%	$207.4736	$207.47	$207.45	$207.50
Purchase #7	$171.98	7.754%	$185.3153	$185.32	$185.30	$185.30
7 purchase totals =	$937.39		$1,005.4997	$1,005.50	$1,005.40	$1,005.60