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	$66.88	8.746%	$72.7293	$72.73	$72.75	$72.70
Purchase #2	$248.63	13.492%	$282.1752	$282.18	$282.20	$282.20
Purchase #3	$247.51	9.124%	$270.0928	$270.09	$270.10	$270.10
Purchase #4	$247.50	3.161%	$255.3235	$255.32	$255.30	$255.30
Purchase #5	$145.68	4.339%	$152.0011	$152.00	$152.00	$152.00
Purchase #6	$46.74	10.644%	$51.715	$51.72	$51.70	$51.70
Purchase #7	$15.85	4.618%	$16.582	$16.58	$16.60	$16.60
7 purchase totals =	$1,018.79		$1,100.6189	$1,100.62	$1,100.65	$1,100.60