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	$11.45	9.375%	$12.5234	$12.52	$12.50	$12.50
Purchase #2	$58.25	12.515%	$65.54	$65.54	$65.55	$65.50
Purchase #3	$138.64	10.706%	$153.4828	$153.48	$153.50	$153.50
Purchase #4	$115.38	13.386%	$130.8248	$130.82	$130.80	$130.80
Purchase #5	$192.31	11.299%	$214.0391	$214.04	$214.05	$214.00
Purchase #6	$227.37	3.862%	$236.151	$236.15	$236.15	$236.20
Purchase #7	$233.60	11.252%	$259.8847	$259.88	$259.90	$259.90
7 purchase totals =	$977.00		$1,072.4458	$1,072.43	$1,072.45	$1,072.40