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	$244.82	6.241%	$260.0992	$260.10	$260.10	$260.10
Purchase #2	$53.90	9.626%	$59.0884	$59.09	$59.10	$59.10
Purchase #3	$79.77	6.102%	$84.6376	$84.64	$84.65	$84.60
Purchase #4	$161.31	6.332%	$171.5241	$171.52	$171.50	$171.50
Purchase #5	$188.87	10.627%	$208.9412	$208.94	$208.95	$208.90
Purchase #6	$183.60	8.486%	$199.1803	$199.18	$199.20	$199.20
Purchase #7	$30.94	6.339%	$32.9013	$32.90	$32.90	$32.90
7 purchase totals =	$943.21		$1,016.3721	$1,016.37	$1,016.40	$1,016.30