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	$84.41	9.467%	$92.4011	$92.40	$92.40	$92.40
Purchase #2	$46.47	12.816%	$52.4256	$52.43	$52.45	$52.40
Purchase #3	$138.41	7.541%	$148.8475	$148.85	$148.85	$148.80
Purchase #4	$149.51	10.707%	$165.518	$165.52	$165.50	$165.50
Purchase #5	$58.34	13.144%	$66.0082	$66.01	$66.00	$66.00
Purchase #6	$46.42	8.441%	$50.3383	$50.34	$50.35	$50.30
Purchase #7	$112.29	12.742%	$126.598	$126.60	$126.60	$126.60
7 purchase totals =	$635.85		$702.1367	$702.15	$702.15	$702.00