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	$169.91	10.226%	$187.285	$187.29	$187.30	$187.30
Purchase #2	$142.45	7.514%	$153.1537	$153.15	$153.15	$153.20
Purchase #3	$64.90	11.500%	$72.3635	$72.36	$72.35	$72.40
Purchase #4	$87.72	6.632%	$93.5376	$93.54	$93.55	$93.50
Purchase #5	$149.40	4.302%	$155.8272	$155.83	$155.85	$155.80
Purchase #6	$161.29	6.811%	$172.2755	$172.28	$172.30	$172.30
Purchase #7	$219.77	5.102%	$230.9827	$230.98	$231.00	$231.00
7 purchase totals =	$995.44		$1,065.4252	$1,065.43	$1,065.50	$1,065.50