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	$34.39	11.547%	$38.361	$38.36	$38.35	$38.40
Purchase #2	$142.84	3.864%	$148.3593	$148.36	$148.35	$148.40
Purchase #3	$244.48	7.600%	$263.0605	$263.06	$263.05	$263.10
Purchase #4	$233.82	10.564%	$258.5207	$258.52	$258.50	$258.50
Purchase #5	$132.33	13.340%	$149.9828	$149.98	$150.00	$150.00
Purchase #6	$72.58	8.171%	$78.5105	$78.51	$78.50	$78.50
Purchase #7	$40.54	12.676%	$45.6789	$45.68	$45.70	$45.70
7 purchase totals =	$900.98		$982.4737	$982.47	$982.45	$982.60