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	$182.80	12.406%	$205.4782	$205.48	$205.50	$205.50
Purchase #2	$137.40	11.525%	$153.2354	$153.24	$153.25	$153.20
Purchase #3	$228.59	5.813%	$241.8779	$241.88	$241.90	$241.90
Purchase #4	$7.25	12.801%	$8.1781	$8.18	$8.20	$8.20
Purchase #5	$223.25	4.654%	$233.6401	$233.64	$233.65	$233.60
Purchase #6	$62.88	5.658%	$66.4378	$66.44	$66.45	$66.40
Purchase #7	$149.54	11.308%	$166.45	$166.45	$166.45	$166.50
7 purchase totals =	$991.71		$1,075.2975	$1,075.31	$1,075.40	$1,075.30