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	$93.88	12.111%	$105.2498	$105.25	$105.25	$105.20
Purchase #2	$35.76	5.555%	$37.7465	$37.75	$37.75	$37.70
Purchase #3	$215.97	7.237%	$231.5997	$231.60	$231.60	$231.60
Purchase #4	$108.63	12.720%	$122.4477	$122.45	$122.45	$122.40
Purchase #5	$37.92	12.730%	$42.7472	$42.75	$42.75	$42.70
Purchase #6	$213.83	12.835%	$241.2751	$241.28	$241.30	$241.30
Purchase #7	$202.31	13.152%	$228.9178	$228.92	$228.90	$228.90
7 purchase totals =	$908.30		$1,009.9838	$1,010.00	$1,010.00	$1,009.80