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	$210.30	11.613%	$234.7221	$234.72	$234.70	$234.70
Purchase #2	$78.75	8.337%	$85.3154	$85.32	$85.30	$85.30
Purchase #3	$54.89	7.399%	$58.9513	$58.95	$58.95	$59.00
Purchase #4	$195.78	7.358%	$210.1855	$210.19	$210.20	$210.20
Purchase #5	$146.81	10.257%	$161.8683	$161.87	$161.85	$161.90
Purchase #6	$127.76	12.529%	$143.7671	$143.77	$143.75	$143.80
Purchase #7	$119.42	6.813%	$127.5561	$127.56	$127.55	$127.60
7 purchase totals =	$933.71		$1,022.3658	$1,022.38	$1,022.30	$1,022.50