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	$249.60	7.825%	$269.1312	$269.13	$269.15	$269.10
Purchase #2	$16.29	7.552%	$17.5202	$17.52	$17.50	$17.50
Purchase #3	$32.42	13.475%	$36.7886	$36.79	$36.80	$36.80
Purchase #4	$137.40	4.744%	$143.9183	$143.92	$143.90	$143.90
Purchase #5	$41.40	9.244%	$45.227	$45.23	$45.25	$45.20
Purchase #6	$134.79	10.309%	$148.6855	$148.69	$148.70	$148.70
Purchase #7	$102.37	3.381%	$105.8311	$105.83	$105.85	$105.80
7 purchase totals =	$714.27		$767.1019	$767.11	$767.15	$767.00