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	$142.75	6.455%	$151.9645	$151.96	$151.95	$152.00
Purchase #2	$130.51	9.265%	$142.6018	$142.60	$142.60	$142.60
Purchase #3	$38.86	6.169%	$41.2573	$41.26	$41.25	$41.30
Purchase #4	$73.61	13.255%	$83.367	$83.37	$83.35	$83.40
Purchase #5	$113.33	4.602%	$118.5454	$118.55	$118.55	$118.50
Purchase #6	$75.49	3.683%	$78.2703	$78.27	$78.25	$78.30
Purchase #7	$246.47	7.665%	$265.3619	$265.36	$265.35	$265.40
7 purchase totals =	$821.02		$881.3682	$881.37	$881.30	$881.50