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	$37.25	3.704%	$38.6297	$38.63	$38.65	$38.60
Purchase #2	$34.85	12.525%	$39.215	$39.22	$39.20	$39.20
Purchase #3	$184.93	7.318%	$198.4632	$198.46	$198.45	$198.50
Purchase #4	$147.73	13.789%	$168.1005	$168.10	$168.10	$168.10
Purchase #5	$170.32	5.366%	$179.4594	$179.46	$179.45	$179.50
Purchase #6	$157.39	7.425%	$169.0762	$169.08	$169.10	$169.10
Purchase #7	$230.43	11.169%	$256.1667	$256.17	$256.15	$256.20
7 purchase totals =	$962.90		$1,049.1107	$1,049.12	$1,049.10	$1,049.20