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	$43.39	3.364%	$44.8496	$44.85	$44.85	$44.80
Purchase #2	$158.45	5.766%	$167.5862	$167.59	$167.60	$167.60
Purchase #3	$114.59	4.354%	$119.5792	$119.58	$119.60	$119.60
Purchase #4	$113.90	3.708%	$118.1234	$118.12	$118.10	$118.10
Purchase #5	$90.89	7.814%	$97.9921	$97.99	$98.00	$98.00
Purchase #6	$146.27	6.762%	$156.1608	$156.16	$156.15	$156.20
Purchase #7	$227.65	12.768%	$256.7164	$256.72	$256.70	$256.70
7 purchase totals =	$895.14		$961.0077	$961.01	$961.00	$961.00