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	$178.55	5.378%	$188.1524	$188.15	$188.15	$188.20
Purchase #2	$219.64	5.426%	$231.5577	$231.56	$231.55	$231.60
Purchase #3	$177.84	12.140%	$199.4298	$199.43	$199.45	$199.40
Purchase #4	$217.55	5.794%	$230.1548	$230.15	$230.15	$230.20
Purchase #5	$148.29	6.830%	$158.4182	$158.42	$158.40	$158.40
Purchase #6	$65.97	6.366%	$70.1697	$70.17	$70.15	$70.20
Purchase #7	$78.42	13.516%	$89.0192	$89.02	$89.00	$89.00
7 purchase totals =	$1,086.26		$1,166.9018	$1,166.90	$1,166.85	$1,167.00