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	$228.80	9.509%	$250.5566	$250.56	$250.55	$250.60
Purchase #2	$228.89	10.686%	$253.3492	$253.35	$253.35	$253.30
Purchase #3	$15.61	10.717%	$17.2829	$17.28	$17.30	$17.30
Purchase #4	$44.41	7.873%	$47.9064	$47.91	$47.90	$47.90
Purchase #5	$116.85	6.622%	$124.5878	$124.59	$124.60	$124.60
Purchase #6	$174.56	12.404%	$196.2124	$196.21	$196.20	$196.20
Purchase #7	$205.94	13.515%	$233.7728	$233.77	$233.75	$233.80
7 purchase totals =	$1,015.06		$1,123.6681	$1,123.67	$1,123.65	$1,123.70