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	$118.68	4.407%	$123.9102	$123.91	$123.90	$123.90
Purchase #2	$107.76	4.812%	$112.9454	$112.95	$112.95	$112.90
Purchase #3	$44.40	4.738%	$46.5037	$46.50	$46.50	$46.50
Purchase #4	$64.43	11.398%	$71.7737	$71.77	$71.75	$71.80
Purchase #5	$191.93	12.358%	$215.6487	$215.65	$215.65	$215.60
Purchase #6	$205.51	8.475%	$222.927	$222.93	$222.95	$222.90
Purchase #7	$127.58	10.292%	$140.7105	$140.71	$140.70	$140.70
7 purchase totals =	$860.29		$934.4192	$934.42	$934.40	$934.30