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	$66.64	8.723%	$72.453	$72.45	$72.45	$72.50
Purchase #2	$66.59	7.663%	$71.6928	$71.69	$71.70	$71.70
Purchase #3	$160.71	5.327%	$169.271	$169.27	$169.25	$169.30
Purchase #4	$156.51	6.561%	$166.7786	$166.78	$166.80	$166.80
Purchase #5	$218.99	5.733%	$231.5447	$231.54	$231.55	$231.50
Purchase #6	$117.76	4.267%	$122.7848	$122.78	$122.80	$122.80
Purchase #7	$36.55	6.388%	$38.8848	$38.88	$38.90	$38.90
7 purchase totals =	$823.75		$873.4097	$873.39	$873.45	$873.50