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	$150.89	12.628%	$169.9444	$169.94	$169.95	$169.90
Purchase #2	$230.47	3.503%	$238.5434	$238.54	$238.55	$238.50
Purchase #3	$156.79	7.851%	$169.0996	$169.10	$169.10	$169.10
Purchase #4	$214.96	3.588%	$222.6728	$222.67	$222.65	$222.70
Purchase #5	$133.94	8.222%	$144.9525	$144.95	$144.95	$145.00
Purchase #6	$105.43	8.676%	$114.5771	$114.58	$114.60	$114.60
Purchase #7	$203.74	5.723%	$215.4	$215.40	$215.40	$215.40
7 purchase totals =	$1,196.22		$1,275.1898	$1,275.18	$1,275.20	$1,275.20