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	$191.66	11.382%	$213.4747	$213.47	$213.45	$213.50
Purchase #2	$30.25	9.488%	$33.1201	$33.12	$33.10	$33.10
Purchase #3	$12.77	4.144%	$13.2992	$13.30	$13.30	$13.30
Purchase #4	$154.48	4.743%	$161.807	$161.81	$161.80	$161.80
Purchase #5	$246.46	13.450%	$279.6089	$279.61	$279.60	$279.60
Purchase #6	$249.56	12.275%	$280.1935	$280.19	$280.20	$280.20
Purchase #7	$127.51	3.773%	$132.321	$132.32	$132.30	$132.30
7 purchase totals =	$1,012.69		$1,113.8244	$1,113.82	$1,113.75	$1,113.80