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	$82.63	12.484%	$92.9455	$92.95	$92.95	$92.90
Purchase #2	$230.97	4.818%	$242.0981	$242.10	$242.10	$242.10
Purchase #3	$34.90	7.125%	$37.3866	$37.39	$37.40	$37.40
Purchase #4	$103.59	7.169%	$111.0164	$111.02	$111.00	$111.00
Purchase #5	$104.60	7.849%	$112.8101	$112.81	$112.80	$112.80
Purchase #6	$40.61	10.403%	$44.8347	$44.83	$44.85	$44.80
Purchase #7	$225.35	6.768%	$240.6017	$240.60	$240.60	$240.60
7 purchase totals =	$822.65		$881.6931	$881.70	$881.70	$881.60