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	$172.66	13.812%	$196.5078	$196.51	$196.50	$196.50
Purchase #2	$117.39	13.606%	$133.3621	$133.36	$133.35	$133.40
Purchase #3	$53.29	10.333%	$58.7965	$58.80	$58.80	$58.80
Purchase #4	$100.55	13.339%	$113.9624	$113.96	$113.95	$114.00
Purchase #5	$184.89	13.525%	$209.8964	$209.90	$209.90	$209.90
Purchase #6	$225.60	9.689%	$247.4584	$247.46	$247.45	$247.50
Purchase #7	$54.96	5.720%	$58.1037	$58.10	$58.10	$58.10
7 purchase totals =	$909.34		$1,018.0873	$1,018.09	$1,018.05	$1,018.20