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	$210.33	12.726%	$237.0966	$237.10	$237.10	$237.10
Purchase #2	$114.46	11.782%	$127.9457	$127.95	$127.95	$127.90
Purchase #3	$44.49	5.393%	$46.8893	$46.89	$46.90	$46.90
Purchase #4	$238.92	7.206%	$256.1366	$256.14	$256.15	$256.10
Purchase #5	$97.33	12.103%	$109.1098	$109.11	$109.10	$109.10
Purchase #6	$173.45	13.206%	$196.3558	$196.36	$196.35	$196.40
Purchase #7	$140.27	11.703%	$156.6858	$156.69	$156.70	$156.70
7 purchase totals =	$1,019.25		$1,130.2196	$1,130.24	$1,130.25	$1,130.20