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	$161.32	6.783%	$172.2623	$172.26	$172.25	$172.30
Purchase #2	$92.31	7.664%	$99.3846	$99.38	$99.40	$99.40
Purchase #3	$97.56	7.646%	$105.0194	$105.02	$105.00	$105.00
Purchase #4	$38.65	8.333%	$41.8707	$41.87	$41.85	$41.90
Purchase #5	$46.53	3.587%	$48.199	$48.20	$48.20	$48.20
Purchase #6	$6.94	13.794%	$7.8973	$7.90	$7.90	$7.90
Purchase #7	$41.58	4.657%	$43.5164	$43.52	$43.50	$43.50
7 purchase totals =	$484.89		$518.1497	$518.15	$518.10	$518.20