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	$212.35	6.364%	$225.864	$225.86	$225.85	$225.90
Purchase #2	$139.83	10.221%	$154.122	$154.12	$154.10	$154.10
Purchase #3	$42.48	9.169%	$46.375	$46.38	$46.40	$46.40
Purchase #4	$80.30	12.212%	$90.1062	$90.11	$90.10	$90.10
Purchase #5	$155.58	8.500%	$168.8043	$168.80	$168.80	$168.80
Purchase #6	$40.32	9.642%	$44.2077	$44.21	$44.20	$44.20
Purchase #7	$136.85	5.823%	$144.8188	$144.82	$144.80	$144.80
7 purchase totals =	$807.71		$874.2980	$874.30	$874.25	$874.30