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	$114.60	10.769%	$126.9413	$126.94	$126.95	$126.90
Purchase #2	$66.47	13.790%	$75.6362	$75.64	$75.65	$75.60
Purchase #3	$210.85	4.319%	$219.9566	$219.96	$219.95	$220.00
Purchase #4	$37.59	3.242%	$38.8087	$38.81	$38.80	$38.80
Purchase #5	$100.65	10.693%	$111.4125	$111.41	$111.40	$111.40
Purchase #6	$154.29	6.757%	$164.7154	$164.72	$164.70	$164.70
Purchase #7	$112.40	7.527%	$120.8603	$120.86	$120.85	$120.90
7 purchase totals =	$796.85		$858.3310	$858.34	$858.30	$858.30