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	$240.76	11.295%	$267.9538	$267.95	$267.95	$268.00
Purchase #2	$211.89	11.123%	$235.4585	$235.46	$235.45	$235.50
Purchase #3	$22.93	5.853%	$24.2721	$24.27	$24.25	$24.30
Purchase #4	$140.84	11.172%	$156.5746	$156.57	$156.55	$156.60
Purchase #5	$59.94	3.140%	$61.8221	$61.82	$61.80	$61.80
Purchase #6	$113.78	3.402%	$117.6508	$117.65	$117.65	$117.70
Purchase #7	$241.57	7.467%	$259.608	$259.61	$259.60	$259.60
7 purchase totals =	$1,031.71		$1,123.3399	$1,123.33	$1,123.25	$1,123.50