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	$59.73	13.613%	$67.861	$67.86	$67.85	$67.90
Purchase #2	$84.79	5.254%	$89.2449	$89.24	$89.25	$89.20
Purchase #3	$19.72	7.546%	$21.2081	$21.21	$21.20	$21.20
Purchase #4	$117.52	13.583%	$133.4827	$133.48	$133.50	$133.50
Purchase #5	$211.62	7.286%	$227.0386	$227.04	$227.05	$227.00
Purchase #6	$230.86	10.670%	$255.4928	$255.49	$255.50	$255.50
Purchase #7	$248.35	4.488%	$259.4959	$259.50	$259.50	$259.50
7 purchase totals =	$972.59		$1,053.8240	$1,053.82	$1,053.85	$1,053.80