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	$208.79	9.422%	$228.4622	$228.46	$228.45	$228.50
Purchase #2	$172.83	5.460%	$182.2665	$182.27	$182.25	$182.30
Purchase #3	$84.62	5.718%	$89.4586	$89.46	$89.45	$89.50
Purchase #4	$38.33	13.248%	$43.408	$43.41	$43.40	$43.40
Purchase #5	$75.56	10.526%	$83.5134	$83.51	$83.50	$83.50
Purchase #6	$117.41	5.749%	$124.1599	$124.16	$124.15	$124.20
Purchase #7	$142.76	8.177%	$154.4335	$154.43	$154.45	$154.40
7 purchase totals =	$840.30		$905.7021	$905.70	$905.65	$905.80