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	$68.94	13.575%	$78.2986	$78.30	$78.30	$78.30
Purchase #2	$196.40	6.586%	$209.3349	$209.33	$209.35	$209.30
Purchase #3	$133.65	13.320%	$151.4522	$151.45	$151.45	$151.50
Purchase #4	$130.91	5.670%	$138.3326	$138.33	$138.35	$138.30
Purchase #5	$179.60	4.871%	$188.3483	$188.35	$188.35	$188.30
Purchase #6	$12.88	8.312%	$13.9506	$13.95	$13.95	$14.00
Purchase #7	$246.85	6.720%	$263.4383	$263.44	$263.45	$263.40
7 purchase totals =	$969.23		$1,043.1555	$1,043.15	$1,043.20	$1,043.10