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	$21.30	9.687%	$23.3633	$23.36	$23.35	$23.40
Purchase #2	$177.48	10.494%	$196.1048	$196.10	$196.10	$196.10
Purchase #3	$193.81	10.556%	$214.2686	$214.27	$214.25	$214.30
Purchase #4	$36.39	3.381%	$37.6203	$37.62	$37.60	$37.60
Purchase #5	$65.82	10.335%	$72.6225	$72.62	$72.60	$72.60
Purchase #6	$235.94	9.386%	$258.0853	$258.09	$258.10	$258.10
Purchase #7	$194.57	10.464%	$214.9298	$214.93	$214.95	$214.90
7 purchase totals =	$925.31		$1,016.9946	$1,016.99	$1,016.95	$1,017.00