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	$83.30	10.492%	$92.0398	$92.04	$92.05	$92.00
Purchase #2	$33.82	13.857%	$38.5064	$38.51	$38.50	$38.50
Purchase #3	$155.80	12.105%	$174.6596	$174.66	$174.65	$174.70
Purchase #4	$116.62	5.800%	$123.384	$123.38	$123.40	$123.40
Purchase #5	$67.90	5.158%	$71.4023	$71.40	$71.40	$71.40
Purchase #6	$29.87	3.527%	$30.9235	$30.92	$30.90	$30.90
Purchase #7	$124.77	5.835%	$132.0503	$132.05	$132.05	$132.10
7 purchase totals =	$612.08		$662.9659	$662.96	$662.95	$663.00