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	$106.38	5.462%	$112.1905	$112.19	$112.20	$112.20
Purchase #2	$92.64	5.632%	$97.8575	$97.86	$97.85	$97.90
Purchase #3	$217.64	10.753%	$241.0428	$241.04	$241.05	$241.00
Purchase #4	$109.69	11.685%	$122.5073	$122.51	$122.50	$122.50
Purchase #5	$82.64	4.767%	$86.5794	$86.58	$86.60	$86.60
Purchase #6	$73.61	12.230%	$82.6125	$82.61	$82.60	$82.60
Purchase #7	$232.60	11.702%	$259.8189	$259.82	$259.80	$259.80
7 purchase totals =	$915.20		$1,002.6089	$1,002.61	$1,002.60	$1,002.60