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	$135.80	10.482%	$150.0346	$150.03	$150.05	$150.00
Purchase #2	$101.82	10.535%	$112.5467	$112.55	$112.55	$112.50
Purchase #3	$188.56	4.257%	$196.587	$196.59	$196.60	$196.60
Purchase #4	$235.47	13.270%	$266.7169	$266.72	$266.70	$266.70
Purchase #5	$6.98	9.659%	$7.6542	$7.65	$7.65	$7.70
Purchase #6	$112.63	8.235%	$121.9051	$121.91	$121.90	$121.90
Purchase #7	$164.56	6.602%	$175.4243	$175.42	$175.40	$175.40
7 purchase totals =	$945.82		$1,030.8688	$1,030.87	$1,030.85	$1,030.80