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	$69.58	13.259%	$78.8056	$78.81	$78.80	$78.80
Purchase #2	$174.33	4.152%	$181.5682	$181.57	$181.55	$181.60
Purchase #3	$78.69	3.563%	$81.4937	$81.49	$81.50	$81.50
Purchase #4	$193.34	12.420%	$217.3528	$217.35	$217.35	$217.40
Purchase #5	$68.34	6.615%	$72.8607	$72.86	$72.85	$72.90
Purchase #6	$192.60	12.324%	$216.336	$216.34	$216.35	$216.30
Purchase #7	$74.67	4.286%	$77.8704	$77.87	$77.85	$77.90
7 purchase totals =	$851.55		$926.2874	$926.29	$926.25	$926.40