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	$22.77	5.224%	$23.9595	$23.96	$23.95	$24.00
Purchase #2	$116.79	12.291%	$131.1447	$131.14	$131.15	$131.10
Purchase #3	$47.68	13.196%	$53.9719	$53.97	$53.95	$54.00
Purchase #4	$38.50	5.218%	$40.5089	$40.51	$40.50	$40.50
Purchase #5	$219.47	3.615%	$227.4038	$227.40	$227.40	$227.40
Purchase #6	$86.59	4.276%	$90.2926	$90.29	$90.30	$90.30
Purchase #7	$104.74	6.252%	$111.2883	$111.29	$111.30	$111.30
7 purchase totals =	$636.54		$678.5697	$678.56	$678.55	$678.60