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	$177.97	7.651%	$191.5865	$191.59	$191.60	$191.60
Purchase #2	$132.55	5.260%	$139.5221	$139.52	$139.50	$139.50
Purchase #3	$96.37	7.789%	$103.8763	$103.88	$103.90	$103.90
Purchase #4	$201.42	12.598%	$226.7949	$226.79	$226.80	$226.80
Purchase #5	$131.83	7.431%	$141.6263	$141.63	$141.65	$141.60
Purchase #6	$94.80	13.309%	$107.4169	$107.42	$107.40	$107.40
Purchase #7	$150.60	3.828%	$156.365	$156.37	$156.35	$156.40
7 purchase totals =	$985.54		$1,067.1880	$1,067.20	$1,067.20	$1,067.20