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	$94.32	5.113%	$99.1426	$99.14	$99.15	$99.10
Purchase #2	$203.56	13.672%	$231.3907	$231.39	$231.40	$231.40
Purchase #3	$190.93	4.743%	$199.9858	$199.99	$200.00	$200.00
Purchase #4	$94.85	5.873%	$100.4205	$100.42	$100.40	$100.40
Purchase #5	$40.85	9.758%	$44.8361	$44.84	$44.85	$44.80
Purchase #6	$145.60	6.176%	$154.5923	$154.59	$154.60	$154.60
Purchase #7	$185.26	10.127%	$204.0213	$204.02	$204.00	$204.00
7 purchase totals =	$955.37		$1,034.3893	$1,034.39	$1,034.40	$1,034.30