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	$156.96	7.464%	$168.6755	$168.68	$168.70	$168.70
Purchase #2	$101.70	9.225%	$111.0818	$111.08	$111.10	$111.10
Purchase #3	$38.85	9.509%	$42.5442	$42.54	$42.55	$42.50
Purchase #4	$96.92	8.733%	$105.384	$105.38	$105.40	$105.40
Purchase #5	$243.80	6.496%	$259.6372	$259.64	$259.65	$259.60
Purchase #6	$95.55	7.779%	$102.9828	$102.98	$103.00	$103.00
Purchase #7	$78.48	8.133%	$84.8628	$84.86	$84.85	$84.90
7 purchase totals =	$812.26		$875.1683	$875.16	$875.25	$875.20