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	$55.95	5.709%	$59.1442	$59.14	$59.15	$59.10
Purchase #2	$231.72	10.347%	$255.6961	$255.70	$255.70	$255.70
Purchase #3	$171.85	6.371%	$182.7986	$182.80	$182.80	$182.80
Purchase #4	$73.26	6.612%	$78.104	$78.10	$78.10	$78.10
Purchase #5	$37.53	5.509%	$39.5975	$39.60	$39.60	$39.60
Purchase #6	$190.91	10.465%	$210.8887	$210.89	$210.90	$210.90
Purchase #7	$239.93	6.144%	$254.6713	$254.67	$254.65	$254.70
7 purchase totals =	$1,001.15		$1,080.9004	$1,080.90	$1,080.90	$1,080.90