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	$234.94	12.347%	$263.948	$263.95	$263.95	$263.90
Purchase #2	$66.52	8.324%	$72.0571	$72.06	$72.05	$72.10
Purchase #3	$220.63	10.624%	$244.0697	$244.07	$244.05	$244.10
Purchase #4	$69.33	13.716%	$78.8393	$78.84	$78.85	$78.80
Purchase #5	$65.80	10.128%	$72.4642	$72.46	$72.45	$72.50
Purchase #6	$39.68	6.377%	$42.2104	$42.21	$42.20	$42.20
Purchase #7	$58.32	3.262%	$60.2224	$60.22	$60.20	$60.20
7 purchase totals =	$755.22		$833.8111	$833.81	$833.75	$833.80