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	$118.86	11.181%	$132.1497	$132.15	$132.15	$132.10
Purchase #2	$76.51	11.742%	$85.4938	$85.49	$85.50	$85.50
Purchase #3	$163.93	5.147%	$172.3675	$172.37	$172.35	$172.40
Purchase #4	$77.76	9.613%	$85.2351	$85.24	$85.25	$85.20
Purchase #5	$33.56	4.520%	$35.0769	$35.08	$35.10	$35.10
Purchase #6	$234.40	13.323%	$265.6291	$265.63	$265.65	$265.60
Purchase #7	$91.71	12.866%	$103.5094	$103.51	$103.50	$103.50
7 purchase totals =	$796.73		$879.4615	$879.47	$879.50	$879.40