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	$161.62	11.342%	$179.9509	$179.95	$179.95	$180.00
Purchase #2	$76.54	11.841%	$85.6031	$85.60	$85.60	$85.60
Purchase #3	$222.31	4.863%	$233.1209	$233.12	$233.10	$233.10
Purchase #4	$28.74	9.858%	$31.5732	$31.57	$31.55	$31.60
Purchase #5	$72.83	6.259%	$77.3884	$77.39	$77.40	$77.40
Purchase #6	$87.39	13.664%	$99.331	$99.33	$99.35	$99.30
Purchase #7	$153.50	13.491%	$174.2087	$174.21	$174.20	$174.20
7 purchase totals =	$802.93		$881.1762	$881.17	$881.15	$881.20