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	$233.66	4.128%	$243.3055	$243.31	$243.30	$243.30
Purchase #2	$48.75	5.368%	$51.3669	$51.37	$51.35	$51.40
Purchase #3	$114.78	11.389%	$127.8523	$127.85	$127.85	$127.90
Purchase #4	$211.90	13.278%	$240.0361	$240.04	$240.05	$240.00
Purchase #5	$175.47	6.528%	$186.9247	$186.92	$186.90	$186.90
Purchase #6	$92.98	12.622%	$104.7159	$104.72	$104.70	$104.70
Purchase #7	$71.79	3.678%	$74.4304	$74.43	$74.45	$74.40
7 purchase totals =	$949.33		$1,028.6318	$1,028.64	$1,028.60	$1,028.60