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	$208.58	11.836%	$233.2675	$233.27	$233.25	$233.30
Purchase #2	$53.49	9.529%	$58.5871	$58.59	$58.60	$58.60
Purchase #3	$160.28	11.830%	$179.2411	$179.24	$179.25	$179.20
Purchase #4	$216.52	3.677%	$224.4814	$224.48	$224.50	$224.50
Purchase #5	$42.76	4.807%	$44.8155	$44.82	$44.80	$44.80
Purchase #6	$37.34	8.776%	$40.617	$40.62	$40.60	$40.60
Purchase #7	$237.53	6.337%	$252.5823	$252.58	$252.60	$252.60
7 purchase totals =	$956.50		$1,033.5919	$1,033.60	$1,033.60	$1,033.60