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	$129.76	10.420%	$143.281	$143.28	$143.30	$143.30
Purchase #2	$195.67	4.111%	$203.714	$203.71	$203.70	$203.70
Purchase #3	$48.51	12.203%	$54.4297	$54.43	$54.45	$54.40
Purchase #4	$177.78	11.383%	$198.0167	$198.02	$198.00	$198.00
Purchase #5	$120.97	5.223%	$127.2883	$127.29	$127.30	$127.30
Purchase #6	$50.66	10.382%	$55.9195	$55.92	$55.90	$55.90
Purchase #7	$131.88	13.857%	$150.1546	$150.15	$150.15	$150.20
7 purchase totals =	$855.23		$932.8038	$932.80	$932.80	$932.80