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	$101.95	8.751%	$110.8716	$110.87	$110.85	$110.90
Purchase #2	$57.50	11.121%	$63.8946	$63.89	$63.90	$63.90
Purchase #3	$40.92	5.380%	$43.1215	$43.12	$43.10	$43.10
Purchase #4	$51.28	12.176%	$57.5239	$57.52	$57.50	$57.50
Purchase #5	$211.44	4.817%	$221.6251	$221.63	$221.65	$221.60
Purchase #6	$118.72	7.704%	$127.8662	$127.87	$127.85	$127.90
Purchase #7	$85.73	10.396%	$94.6425	$94.64	$94.65	$94.60
7 purchase totals =	$667.54		$719.5454	$719.54	$719.50	$719.50