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	$154.96	11.181%	$172.2861	$172.29	$172.30	$172.30
Purchase #2	$121.75	4.615%	$127.3688	$127.37	$127.35	$127.40
Purchase #3	$77.80	11.102%	$86.4374	$86.44	$86.45	$86.40
Purchase #4	$220.72	11.195%	$245.4296	$245.43	$245.45	$245.40
Purchase #5	$172.79	11.644%	$192.9097	$192.91	$192.90	$192.90
Purchase #6	$122.35	13.247%	$138.5577	$138.56	$138.55	$138.60
Purchase #7	$39.54	11.335%	$44.0219	$44.02	$44.00	$44.00
7 purchase totals =	$909.91		$1,007.0112	$1,007.02	$1,007.00	$1,007.00