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	$167.75	10.762%	$185.8033	$185.80	$185.80	$185.80
Purchase #2	$126.98	13.121%	$143.641	$143.64	$143.65	$143.60
Purchase #3	$59.93	9.839%	$65.8265	$65.83	$65.85	$65.80
Purchase #4	$126.97	7.805%	$136.88	$136.88	$136.90	$136.90
Purchase #5	$203.58	9.162%	$222.232	$222.23	$222.25	$222.20
Purchase #6	$11.36	6.525%	$12.1012	$12.10	$12.10	$12.10
Purchase #7	$41.40	3.379%	$42.7989	$42.80	$42.80	$42.80
7 purchase totals =	$737.97		$809.2829	$809.28	$809.35	$809.20