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	$187.53	7.422%	$201.4485	$201.45	$201.45	$201.40
Purchase #2	$173.95	4.219%	$181.289	$181.29	$181.30	$181.30
Purchase #3	$232.54	9.874%	$255.501	$255.50	$255.50	$255.50
Purchase #4	$85.35	6.359%	$90.7774	$90.78	$90.80	$90.80
Purchase #5	$141.57	3.782%	$146.9242	$146.92	$146.90	$146.90
Purchase #6	$106.63	13.780%	$121.3236	$121.32	$121.30	$121.30
Purchase #7	$39.70	12.307%	$44.5859	$44.59	$44.60	$44.60
7 purchase totals =	$967.27		$1,041.8496	$1,041.85	$1,041.85	$1,041.80