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	$207.60	7.387%	$222.9354	$222.94	$222.95	$222.90
Purchase #2	$174.51	4.585%	$182.5113	$182.51	$182.50	$182.50
Purchase #3	$58.55	10.298%	$64.5795	$64.58	$64.60	$64.60
Purchase #4	$226.60	5.809%	$239.7632	$239.76	$239.75	$239.80
Purchase #5	$84.56	5.845%	$89.5025	$89.50	$89.50	$89.50
Purchase #6	$149.75	11.309%	$166.6852	$166.69	$166.70	$166.70
Purchase #7	$247.47	13.514%	$280.9131	$280.91	$280.90	$280.90
7 purchase totals =	$1,149.04		$1,246.8902	$1,246.89	$1,246.90	$1,246.90