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	$62.80	10.690%	$69.5133	$69.51	$69.50	$69.50
Purchase #2	$246.82	4.792%	$258.6476	$258.65	$258.65	$258.60
Purchase #3	$83.55	9.624%	$91.5909	$91.59	$91.60	$91.60
Purchase #4	$130.78	13.273%	$148.1384	$148.14	$148.15	$148.10
Purchase #5	$119.81	12.863%	$135.2212	$135.22	$135.20	$135.20
Purchase #6	$247.35	11.211%	$275.0804	$275.08	$275.10	$275.10
Purchase #7	$96.78	12.390%	$108.771	$108.77	$108.75	$108.80
7 purchase totals =	$987.89		$1,086.9628	$1,086.96	$1,086.95	$1,086.90