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	$243.44	6.660%	$259.6531	$259.65	$259.65	$259.70
Purchase #2	$38.98	12.228%	$43.7465	$43.75	$43.75	$43.70
Purchase #3	$152.39	10.787%	$168.8283	$168.83	$168.85	$168.80
Purchase #4	$86.95	3.410%	$89.915	$89.92	$89.90	$89.90
Purchase #5	$124.55	11.342%	$138.6765	$138.68	$138.70	$138.70
Purchase #6	$172.70	10.240%	$190.3845	$190.38	$190.40	$190.40
Purchase #7	$130.98	10.204%	$144.3452	$144.35	$144.35	$144.30
7 purchase totals =	$949.99		$1,035.5491	$1,035.56	$1,035.60	$1,035.50