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	$139.25	13.861%	$158.5514	$158.55	$158.55	$158.60
Purchase #2	$198.80	12.797%	$224.2404	$224.24	$224.25	$224.20
Purchase #3	$178.45	10.723%	$197.5852	$197.59	$197.60	$197.60
Purchase #4	$75.59	4.357%	$78.8835	$78.88	$78.90	$78.90
Purchase #5	$101.86	13.495%	$115.606	$115.61	$115.60	$115.60
Purchase #6	$155.44	7.290%	$166.7716	$166.77	$166.75	$166.80
Purchase #7	$155.34	6.184%	$164.9462	$164.95	$164.95	$164.90
7 purchase totals =	$1,004.73		$1,106.5843	$1,106.59	$1,106.60	$1,106.60