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	$150.76	5.649%	$159.2764	$159.28	$159.30	$159.30
Purchase #2	$124.52	3.137%	$128.4262	$128.43	$128.45	$128.40
Purchase #3	$146.98	13.315%	$166.5504	$166.55	$166.55	$166.60
Purchase #4	$141.59	13.600%	$160.8462	$160.85	$160.85	$160.80
Purchase #5	$211.35	13.397%	$239.6646	$239.66	$239.65	$239.70
Purchase #6	$175.30	5.258%	$184.5173	$184.52	$184.50	$184.50
Purchase #7	$59.54	11.274%	$66.2525	$66.25	$66.25	$66.30
7 purchase totals =	$1,010.04		$1,105.5336	$1,105.54	$1,105.55	$1,105.60