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	$155.58	7.226%	$166.8222	$166.82	$166.80	$166.80
Purchase #2	$56.38	11.482%	$62.8536	$62.85	$62.85	$62.90
Purchase #3	$142.26	10.335%	$156.9626	$156.96	$156.95	$157.00
Purchase #4	$18.90	9.495%	$20.6946	$20.69	$20.70	$20.70
Purchase #5	$189.75	5.859%	$200.8675	$200.87	$200.85	$200.90
Purchase #6	$143.42	7.825%	$154.6426	$154.64	$154.65	$154.60
Purchase #7	$239.42	4.749%	$250.7901	$250.79	$250.80	$250.80
7 purchase totals =	$945.71		$1,013.6332	$1,013.62	$1,013.60	$1,013.70