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	$210.40	13.812%	$239.4604	$239.46	$239.45	$239.50
Purchase #2	$214.56	3.608%	$222.3013	$222.30	$222.30	$222.30
Purchase #3	$133.58	11.521%	$148.9698	$148.97	$148.95	$149.00
Purchase #4	$168.95	12.758%	$190.5046	$190.50	$190.50	$190.50
Purchase #5	$80.75	9.457%	$88.3865	$88.39	$88.40	$88.40
Purchase #6	$85.85	7.655%	$92.4218	$92.42	$92.40	$92.40
Purchase #7	$18.84	13.427%	$21.3696	$21.37	$21.35	$21.40
7 purchase totals =	$912.93		$1,003.4140	$1,003.41	$1,003.35	$1,003.50