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	$71.99	8.699%	$78.2524	$78.25	$78.25	$78.30
Purchase #2	$28.40	3.323%	$29.3437	$29.34	$29.35	$29.30
Purchase #3	$34.66	11.764%	$38.7374	$38.74	$38.75	$38.70
Purchase #4	$102.28	4.626%	$107.0115	$107.01	$107.00	$107.00
Purchase #5	$66.30	9.458%	$72.5707	$72.57	$72.55	$72.60
Purchase #6	$10.79	6.190%	$11.4579	$11.46	$11.45	$11.50
Purchase #7	$37.96	13.112%	$42.9373	$42.94	$42.95	$42.90
7 purchase totals =	$352.38		$380.3109	$380.31	$380.30	$380.30