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	$108.31	5.675%	$114.4566	$114.46	$114.45	$114.50
Purchase #2	$187.51	12.695%	$211.3144	$211.31	$211.30	$211.30
Purchase #3	$41.74	13.506%	$47.3774	$47.38	$47.40	$47.40
Purchase #4	$205.87	5.747%	$217.7013	$217.70	$217.70	$217.70
Purchase #5	$153.42	9.438%	$167.8998	$167.90	$167.90	$167.90
Purchase #6	$179.80	11.653%	$200.7521	$200.75	$200.75	$200.80
Purchase #7	$40.84	7.382%	$43.8548	$43.85	$43.85	$43.90
7 purchase totals =	$917.49		$1,003.3564	$1,003.35	$1,003.35	$1,003.50