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	$184.87	8.258%	$200.1366	$200.14	$200.15	$200.10
Purchase #2	$154.35	4.700%	$161.6045	$161.60	$161.60	$161.60
Purchase #3	$62.84	13.207%	$71.1393	$71.14	$71.15	$71.10
Purchase #4	$231.29	11.771%	$258.5151	$258.52	$258.50	$258.50
Purchase #5	$99.35	5.853%	$105.165	$105.17	$105.15	$105.20
Purchase #6	$144.34	12.839%	$162.8718	$162.87	$162.85	$162.90
Purchase #7	$34.70	11.212%	$38.5906	$38.59	$38.60	$38.60
7 purchase totals =	$911.74		$998.0229	$998.03	$998.00	$998.00