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	$27.28	6.105%	$28.9454	$28.95	$28.95	$28.90
Purchase #2	$37.86	13.780%	$43.0771	$43.08	$43.10	$43.10
Purchase #3	$101.91	11.365%	$113.4921	$113.49	$113.50	$113.50
Purchase #4	$13.64	10.695%	$15.0988	$15.10	$15.10	$15.10
Purchase #5	$78.55	5.296%	$82.71	$82.71	$82.70	$82.70
Purchase #6	$140.40	9.835%	$154.2083	$154.21	$154.20	$154.20
Purchase #7	$218.73	5.209%	$230.1236	$230.12	$230.10	$230.10
7 purchase totals =	$618.37		$667.6553	$667.66	$667.65	$667.60