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	$194.84	5.268%	$205.1042	$205.10	$205.10	$205.10
Purchase #2	$153.69	11.317%	$171.0831	$171.08	$171.10	$171.10
Purchase #3	$150.29	13.630%	$170.7745	$170.77	$170.75	$170.80
Purchase #4	$182.41	7.788%	$196.6161	$196.62	$196.60	$196.60
Purchase #5	$42.25	9.693%	$46.3453	$46.35	$46.35	$46.30
Purchase #6	$181.29	10.694%	$200.6772	$200.68	$200.70	$200.70
Purchase #7	$22.95	8.405%	$24.8789	$24.88	$24.90	$24.90
7 purchase totals =	$927.72		$1,015.4793	$1,015.48	$1,015.50	$1,015.50