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	$147.47	4.488%	$154.0885	$154.09	$154.10	$154.10
Purchase #2	$205.91	10.162%	$226.8346	$226.83	$226.85	$226.80
Purchase #3	$161.62	12.663%	$182.0859	$182.09	$182.10	$182.10
Purchase #4	$78.73	5.871%	$83.3522	$83.35	$83.35	$83.40
Purchase #5	$52.56	4.812%	$55.0892	$55.09	$55.10	$55.10
Purchase #6	$113.28	8.647%	$123.0753	$123.08	$123.10	$123.10
Purchase #7	$237.61	10.442%	$262.4212	$262.42	$262.40	$262.40
7 purchase totals =	$997.18		$1,086.9469	$1,086.95	$1,087.00	$1,087.00