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	$185.31	9.868%	$203.5964	$203.60	$203.60	$203.60
Purchase #2	$230.95	13.855%	$262.9481	$262.95	$262.95	$262.90
Purchase #3	$18.44	10.467%	$20.3701	$20.37	$20.35	$20.40
Purchase #4	$74.59	4.856%	$78.2121	$78.21	$78.20	$78.20
Purchase #5	$213.45	8.406%	$231.3926	$231.39	$231.40	$231.40
Purchase #6	$90.90	5.663%	$96.0477	$96.05	$96.05	$96.00
Purchase #7	$147.45	7.686%	$158.783	$158.78	$158.80	$158.80
7 purchase totals =	$961.09		$1,051.3500	$1,051.35	$1,051.35	$1,051.30