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	$176.53	7.758%	$190.2252	$190.23	$190.25	$190.20
Purchase #2	$112.95	7.180%	$121.0598	$121.06	$121.05	$121.10
Purchase #3	$56.87	4.461%	$59.407	$59.41	$59.40	$59.40
Purchase #4	$172.44	10.699%	$190.8894	$190.89	$190.90	$190.90
Purchase #5	$115.83	7.705%	$124.7547	$124.75	$124.75	$124.80
Purchase #6	$122.96	5.156%	$129.2998	$129.30	$129.30	$129.30
Purchase #7	$225.32	3.769%	$233.8123	$233.81	$233.80	$233.80
7 purchase totals =	$982.90		$1,049.4482	$1,049.45	$1,049.45	$1,049.50