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	$167.77	4.841%	$175.8917	$175.89	$175.90	$175.90
Purchase #2	$16.83	6.744%	$17.965	$17.97	$17.95	$18.00
Purchase #3	$138.38	3.403%	$143.0891	$143.09	$143.10	$143.10
Purchase #4	$152.40	8.159%	$164.8343	$164.83	$164.85	$164.80
Purchase #5	$83.77	8.123%	$90.5746	$90.57	$90.55	$90.60
Purchase #6	$64.72	13.629%	$73.5407	$73.54	$73.55	$73.50
Purchase #7	$68.93	12.393%	$77.4725	$77.47	$77.45	$77.50
7 purchase totals =	$692.80		$743.3679	$743.36	$743.35	$743.40