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	$196.48	10.720%	$217.5427	$217.54	$217.55	$217.50
Purchase #2	$83.30	6.852%	$89.0077	$89.01	$89.00	$89.00
Purchase #3	$84.64	8.135%	$91.5255	$91.53	$91.55	$91.50
Purchase #4	$200.99	12.172%	$225.4545	$225.45	$225.45	$225.50
Purchase #5	$122.42	11.461%	$136.4506	$136.45	$136.45	$136.50
Purchase #6	$10.85	7.201%	$11.6313	$11.63	$11.65	$11.60
Purchase #7	$23.62	4.537%	$24.6916	$24.69	$24.70	$24.70
7 purchase totals =	$722.30		$796.3039	$796.30	$796.35	$796.30