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	$205.59	3.802%	$213.4065	$213.41	$213.40	$213.40
Purchase #2	$104.97	6.147%	$111.4225	$111.42	$111.40	$111.40
Purchase #3	$172.52	5.527%	$182.0552	$182.06	$182.05	$182.10
Purchase #4	$53.89	7.277%	$57.8116	$57.81	$57.80	$57.80
Purchase #5	$227.45	12.449%	$255.7653	$255.77	$255.75	$255.80
Purchase #6	$14.71	3.669%	$15.2497	$15.25	$15.25	$15.20
Purchase #7	$119.35	5.249%	$125.6147	$125.61	$125.60	$125.60
7 purchase totals =	$898.48		$961.3255	$961.33	$961.25	$961.30