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	$127.83	9.857%	$140.4302	$140.43	$140.45	$140.40
Purchase #2	$100.71	13.274%	$114.0782	$114.08	$114.10	$114.10
Purchase #3	$169.87	12.830%	$191.6643	$191.66	$191.65	$191.70
Purchase #4	$201.32	13.674%	$228.8485	$228.85	$228.85	$228.80
Purchase #5	$175.26	8.353%	$189.8995	$189.90	$189.90	$189.90
Purchase #6	$38.61	9.355%	$42.222	$42.22	$42.20	$42.20
Purchase #7	$122.41	11.484%	$136.4676	$136.47	$136.45	$136.50
7 purchase totals =	$936.01		$1,043.6103	$1,043.61	$1,043.60	$1,043.60