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	$47.75	10.869%	$52.9399	$52.94	$52.95	$52.90
Purchase #2	$71.80	10.834%	$79.5788	$79.58	$79.60	$79.60
Purchase #3	$165.97	3.610%	$171.9615	$171.96	$171.95	$172.00
Purchase #4	$69.27	13.525%	$78.6388	$78.64	$78.65	$78.60
Purchase #5	$181.64	10.806%	$201.268	$201.27	$201.25	$201.30
Purchase #6	$188.69	4.240%	$196.6905	$196.69	$196.70	$196.70
Purchase #7	$13.82	12.128%	$15.4961	$15.50	$15.50	$15.50
7 purchase totals =	$738.94		$796.5736	$796.58	$796.60	$796.60