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	$151.43	10.683%	$167.6073	$167.61	$167.60	$167.60
Purchase #2	$7.35	10.654%	$8.1331	$8.13	$8.15	$8.10
Purchase #3	$57.34	13.664%	$65.1749	$65.17	$65.15	$65.20
Purchase #4	$212.98	9.139%	$232.4442	$232.44	$232.45	$232.40
Purchase #5	$104.90	11.311%	$116.7652	$116.77	$116.75	$116.80
Purchase #6	$18.36	8.833%	$19.9817	$19.98	$20.00	$20.00
Purchase #7	$85.81	5.847%	$90.8273	$90.83	$90.85	$90.80
7 purchase totals =	$638.17		$700.9337	$700.93	$700.95	$700.90