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	$190.67	4.489%	$199.2292	$199.23	$199.25	$199.20
Purchase #2	$21.82	9.209%	$23.8294	$23.83	$23.85	$23.80
Purchase #3	$34.43	10.697%	$38.113	$38.11	$38.10	$38.10
Purchase #4	$22.92	11.738%	$25.6103	$25.61	$25.60	$25.60
Purchase #5	$146.71	7.383%	$157.5416	$157.54	$157.55	$157.50
Purchase #6	$118.55	8.106%	$128.1597	$128.16	$128.15	$128.20
Purchase #7	$74.41	5.574%	$78.5576	$78.56	$78.55	$78.60
7 purchase totals =	$609.51		$651.0408	$651.04	$651.05	$651.00