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	$53.28	11.534%	$59.4253	$59.43	$59.45	$59.40
Purchase #2	$184.95	12.311%	$207.7192	$207.72	$207.70	$207.70
Purchase #3	$130.71	8.181%	$141.4034	$141.40	$141.40	$141.40
Purchase #4	$205.27	11.790%	$229.4713	$229.47	$229.45	$229.50
Purchase #5	$176.86	12.245%	$198.5165	$198.52	$198.50	$198.50
Purchase #6	$204.84	11.249%	$227.8825	$227.88	$227.90	$227.90
Purchase #7	$102.30	13.509%	$116.1197	$116.12	$116.10	$116.10
7 purchase totals =	$1,058.21		$1,180.5379	$1,180.54	$1,180.50	$1,180.50