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	$59.52	6.371%	$63.312	$63.31	$63.30	$63.30
Purchase #2	$70.30	3.528%	$72.7802	$72.78	$72.80	$72.80
Purchase #3	$249.82	5.462%	$263.4652	$263.47	$263.45	$263.50
Purchase #4	$103.76	9.353%	$113.4647	$113.46	$113.45	$113.50
Purchase #5	$183.85	13.823%	$209.2636	$209.26	$209.25	$209.30
Purchase #6	$233.29	8.594%	$253.3389	$253.34	$253.35	$253.30
Purchase #7	$176.63	8.705%	$192.0056	$192.01	$192.00	$192.00
7 purchase totals =	$1,077.17		$1,167.6302	$1,167.63	$1,167.60	$1,167.70