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	$131.36	8.455%	$142.4665	$142.47	$142.45	$142.50
Purchase #2	$90.55	4.429%	$94.5605	$94.56	$94.55	$94.60
Purchase #3	$101.56	8.130%	$109.8168	$109.82	$109.80	$109.80
Purchase #4	$200.40	7.479%	$215.3879	$215.39	$215.40	$215.40
Purchase #5	$197.61	7.609%	$212.6461	$212.65	$212.65	$212.60
Purchase #6	$79.49	12.283%	$89.2538	$89.25	$89.25	$89.30
Purchase #7	$188.69	7.848%	$203.4984	$203.50	$203.50	$203.50
7 purchase totals =	$989.66		$1,067.6300	$1,067.64	$1,067.60	$1,067.70