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	$151.88	12.435%	$170.7663	$170.77	$170.75	$170.80
Purchase #2	$181.27	13.542%	$205.8176	$205.82	$205.80	$205.80
Purchase #3	$22.47	4.106%	$23.3926	$23.39	$23.40	$23.40
Purchase #4	$191.92	9.734%	$210.6015	$210.60	$210.60	$210.60
Purchase #5	$106.49	9.656%	$116.7727	$116.77	$116.75	$116.80
Purchase #6	$173.33	13.170%	$196.1576	$196.16	$196.15	$196.20
Purchase #7	$182.80	13.790%	$208.0081	$208.01	$208.00	$208.00
7 purchase totals =	$1,010.16		$1,131.5164	$1,131.52	$1,131.45	$1,131.60