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	$179.57	3.113%	$185.16	$185.16	$185.15	$185.20
Purchase #2	$139.54	11.719%	$155.8927	$155.89	$155.90	$155.90
Purchase #3	$44.63	11.122%	$49.5937	$49.59	$49.60	$49.60
Purchase #4	$191.97	13.260%	$217.4252	$217.43	$217.45	$217.40
Purchase #5	$153.25	5.372%	$161.4826	$161.48	$161.50	$161.50
Purchase #6	$37.77	8.412%	$40.9472	$40.95	$40.95	$40.90
Purchase #7	$226.97	10.365%	$250.4954	$250.50	$250.50	$250.50
7 purchase totals =	$973.70		$1,060.9968	$1,061.00	$1,061.05	$1,061.00