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	$128.93	9.509%	$141.19	$141.19	$141.20	$141.20
Purchase #2	$164.54	9.234%	$179.7336	$179.73	$179.75	$179.70
Purchase #3	$104.81	13.162%	$118.6051	$118.61	$118.60	$118.60
Purchase #4	$59.38	7.583%	$63.8828	$63.88	$63.90	$63.90
Purchase #5	$36.97	4.279%	$38.5519	$38.55	$38.55	$38.60
Purchase #6	$131.93	4.222%	$137.5001	$137.50	$137.50	$137.50
Purchase #7	$49.90	8.126%	$53.9549	$53.95	$53.95	$54.00
7 purchase totals =	$676.46		$733.4184	$733.41	$733.45	$733.50